By 'research' do you mean reading stuff online? Because that's more an abundance of misinformation, in misconstrued facts, exaggerations and distortions, and straight fiction on that topic. The difference between what random websites say (even serious-seeming ones) and what academics think could hardly be larger.

As I explained in a post just yesterday and other threads before that: We don't know much about what pre-Christian Scandinavians believe. The vast majority of what you're reading about (to the extent that it has got a factual basis) is from two writings by the same guy; the Poetic and Prose Eddas of Snorri Sturluson. Both written at least a century and a half into the Christian era in Iceland, and never intended as an actual documentation of the religion in the first place. The 'symbols' the internet will tell you about are either simply fake or very misrepresented; as I also explained recently there's basically no such thing as a 'valknut' symbol. The 'vegvísir' and 'aegshjalmur' and other symbols taken from modern Icelandic grimoires are of continental Renaissance origin and are thus neither Scandinavian nor of Viking Age origins, and only seem to have been passed off as such through the giant leap-to-conclusions that any folk magic from Iceland must be 'viking'. An even more far-fetched (yet common) thing you'll find online is the claim that Germanic peoples did divination with Elder Futhark runes. Which comes from a claim from Tacitus Germanica (98 CE) claiming they did divination with sticks with symbols on them. Tacitus' accounts are not considered very trustworthy at all in the first place, but this additionally assumes that the 'symbols' in question were letter-runes, and of a set that's not been documented until over a century later. Nevertheless the internet will happily sell you a set of 'divination runes' not based on .. anything really. There are zero texts 'from that time' if you mean things written by actual pre-Christian Scandinavians, except for short and largely-formulaic runestone inscriptions. (and most runestone inscriptions are by christians by a pretty large margin)

The very concept of a single 'Norse Mythology' or at least single pre-Christian religion in Scandinavia is openly under question these days. It was always just an assumption that these 13th century writings from Iceland would represent what people believed in the rest of Scandinavia centuries prior, and that assumption is under a lot of attack as a construct of the 19th century and its Viking Romanticism (responsible for much of the laypersons conception of the Old North that persists to this day)

In 2003, Fredrik Svanberg's massive two-volume thesis Decolonizing the Viking Age showed that that, from archaeological evidence there was in fact massive variation in how religion was practiced even within relatively small regions of Scandinavia. Scania alone had more than half-dozen distinct burial practices in use during the Viking Age. Stefan Brink's survey of theophoric names of Scandinavia (How uniform was Old Norse religion?, 2007) showed great regional variation in which gods seemed to have been important, and also that the Eddas do not appear to represent their importance. There had been, to some extent, a common Germanic pantheon with at least the gods of the week-days (Tyr, Odin, Thor, Frej in Norse terms).

But the Eddas do not tell the whole story; the German Merseburg charms mention the otherwise unknown Sinthgunt. The only certain reference to veneration of Forseti is from Frisia, not Scandinavia. The only reference to Heimdallr outside the Eddas is on a spindle whorl from Linconshire, England, which also mentions Odin and the otherwise unknown þalfa. There's nothing indicating Loki was ever venerated, nor even considered a god outside the context of Eddic stories. (yet Loki is one of only three gods, with Thor and Odin, featured in more than one Eddic myth) Gods like Bragi and Hermodr may not've existed in any form.

There is a lot written about the Eddas and their mythology. In fact any decent book on Norse Mythology will more than cover everything in the Eddas, because the Eddas are not that long, the descriptions are usually short and there's a lot of redundancy since the Prose Edda (being mainly Snorri's own writing) is based off the Poetic Edda (which is Snorri's compilation of writings of older origins). So, for instance, a passing reference to "ski-god" being a nickname for Ullr, who is also described as being good at archery, is frequently extrapolated into Ullr being the god god of skiing and archery. Then there's the Bökingsta runestone that has a figure with skis and a bow-and-arrow in what looks like a hunting scene, and therefore this gets represented in some popular accounts as being a picture of Ullr. Which it might be. My point is that we don't know it to be, the claim is based off a number of assumptions. Popular accounts don't like to delve into uncertainty and how-do-they-know-that about the claims made, so they easily give the impression of more being known that actually is. (and this is far less far-fetched than, for instance, [turning a single vague quote by Ibn Fadlan into the 'fact' of Viking tattoos)

As said, what we actually know for certain is quite limited, and not necessarily that much more for Norse mythology than for the Anglo-Saxons or other Germanic peoples. Because the Eddas are where most materials are coming from (not counting the purely invented stuff various 'enthusiasts' have come up with), and the Eddas are not that reliable. Now, don't get me wrong: The Eddas are still very important as sources, not least of folklore. And they're of course infinitely better than having nothing at all. But a key difference in academic-vs-popular depictions is that the latter take them at face value, practically elevating them to 'canonical scripture' (when they had a status as neither). Another difference between the mythologies is that there's no "Edda" from any place other than Iceland. They are the result of Iceland having an unusually literate culture (e.g. recording and preserving many sagas as well), not Iceland being more pagan or some such (Sweden converted significantly later) There's the Niebelungenlied from Germany, showing the Siegfried/Sigurd story in the Eddas was popular there too in the 13th century, and also evidence from Sweden and Norway showing that story was still popular there at that time too. There are picture stones and the occasional runestone of the Viking Age showing identifiable Eddic motifs, but there are also many motifs on them which have no obvious identification that we know of, but which were likely well-known to the stone's contemporaries. Although the truth of the Eddas is hard to evaluate on their own, where there are such identifiable motifs they do give clues to folklore and religious motifs of the Viking Age.

But Germany had been converted by the Viking Age. The Eddas are twice as far removed in time from German paganism than from Scandinavian. So even ignoring the geographic factor they're not as a good a guide there either in theory or in practice.

A I've said in earlier posts, what we know from primary sources is not that much and a fragmentary and incomplete picture of religion that was heterogeneous with time, place and probably also social class. In this it is not all that different from the situation with the Germanic parts of the continent. Certainly not as different as it would appear from taking the Eddas at face value as a guide to the religion. A hundred web pages saying vikings went to Valhalla may seem to give the image of great certainty about Old Norse conceptions of the afterlife (for instance), but we really have no idea. Even the Eddas seem self-contradictory about it.

/u/PlatypusKeeper has already done an excellent job dissecting what pop-history thinks it knows about Norse mythology, so I thought I'd touch briefly on another part of your question: our dearth of knowledge of pre-Christian Germanic mythology.

The first thing we need to consider is that literature in early medieval Europe is overwhelmingly Christian in its provenance. That's not to say that every work was itself theological at all, but that the circumstances of its production were almost intrinsically linked to Christian writers, especially in the case of historical and anthropological works. The Sagas from which people claim knowledge of Norse mythology, for example, are almost certainly written by Christian monks. The simple truth with pre-Christian mythologies is that in many cases, they simply aren't deemed worth recording, and contemporary Paganisms are usually only recorded if there is a moral lesson to be imparted or the information is deemed useful.

Pope Gregory's correspondence with Augustine of Canterbury is notable in its instruction that conversion be facilitated by co-opting pre-existing feasts and festivals and repurposing them for Christian celebrations. Not least, this is the source of frequent neo-Pagan claims that Christianity is somehow stolen from Pagan societies. A frequent offender is Easter. Bede, in his Historia Ecclesiastica tells the reader that the Christian festival of Pascha is vaguely analogous, in both timing and purpose, to the Pagan festival of Eostremonađ with which their ancestors may have been familiar. From this we can infer the existance of a Northumbrian Anglian pre-Christian deity known as Eostre who was fêted in the Spring, most likely in the context of post-Winter renewal. Further claims - that she was some kind of 'Mother Earth' fertility goddess celebrated throughout pre-Christian Germanic society, are entitely supposition borne largely from early modern romanticism.

In the late 12th Century, Gerald of Wales' Topographia Hibernica accounts a number of supposed Irish 'Pagan' ceremonies, but these are vitriolic works designed explicitly to legitimise the Cambro-Norman conquest of Ireland by portraying the Irish as a savage and bestial people. Adam of Bremen's famous account of Norse sacrifice and worship at Uppsala is designed more to illustrate the barbarous savagery of the North than to actually inform - and is lifted heavily from Pliny the Elder to do so - and is quite possibly an excuse for why Adam isn't converting the Swedish.

Thietmar of Merseburg's Chronicon actually contains a fairly in-depth and realistic portrayal of the religious sites, rites and practices of the Wendish people East of Merseburg, but this is by far the exception to the rule, and its clear that Thietmar has a real, anthropological interest in these people.