English is a hodgepodge of many different linguistic inputs. Its base is Germanic, via Middle English (Chaucer) and Old English (Beowulf). Germanic tribes crossed over to the British Isles at the end of antiquity, defeating, absorbing, and/or incorporating the native Brythonic residents. These tribes were the Angols, Saxons, and Jutes, forming what is later commonly called the Anglo-Saxon culture. They spoke Germanic languages which became marked by Celtic/Brythonic. Anglo-Saxon also retained some Latin words from Britain's erstwhile status as a Roman province, though not nearly as many as their Germanic cousins in Europe (like the Goths or Franks).

As Anglo-Saxon "English" developed, it was heavily influenced by the Romance Languages, especially early and middle French. When William the Conqueror arrived in Britain after the battle of Hastings in 1066, he accelerated a process of linguistic mixing (ie French speakers were introduced to the Isles). This process was already happening via frequent trading and cross-channel migration even before this. French is very close to Latin, if you don't pay too much attention to spellings. On top of the French mixing, English also imported many Latin words wholesale. Writers like Shakespeare helped this along. During this process, analogized Latinate words were also created—in other words, new, non-Latin words were built and incorporated based loosely on the rules of Latin. So for instance, in English, I can talk about the "cyberpunkification" of science fiction. "cyberpunk" is a wholly modern term, but I can add "-fication" to the end to indicate a process, from the Latin -fac "to do, make". Any English word that ends in -tion is either an actual Latin word, or else a "fake" Latin word built on Latin's rules (-io is a common Latin nound ending; cf natio, oratio, constipatio).

This is a difficult question to answer, especially since most historians are not qualified linguists. But as someone with a history degree and someone who speaks both English and Dutch, I will attempt to answer this to the best of my abilities. I will preface this by saying I am not in any way a qualified linguist, and most of this is newish material to me. We will start by saying that there is no “if” in terms of English being a Germanic language. It simply is.

English has the grammatical structure of a typical West Germanic language, which includes English, Dutch, and German. The closest lingual cousins to English are Dutch and Frisian (sometimes considered a dialect of Dutch). You can see many similarities between these languages, such as in anatomy (hand-hand, tand-tooth, vinger-finger) and in common nouns (zuster-sister, broer-brother, vader-father).

Latin has some presence in most European languages, but you are correct in observing that it is more present in English than in other Germanic languages. A cursory glance through some textbooks and general histories has indicated to me that this is mainly due to the influence of the Normans on English history. William the Conquerer brought the Norman language with him to England, which was a kind of Proto-French, which in turn became Anglo-Norman. This language was used in the British Isles throughout the first half of the last millennium, and eventually gave way to modern English. Its influence permanently changed the progression of the English language, however.

We see many remnants of this influence in modern English. Some of the most obvious ones are words like beef (Old French: boef), pork (Old French: porc). Some very commonly used words in English might be less obviously French in origin, such as port, strange, distance, liberty and incredible. Here we begin to see how prevalent Anglo-Norman really is in our modern language.

Even considering all this influence, English still maintains its status as a West-Germanic language. Many sources explain this by saying that the influence of Old French on English is purely lexical (only vocabulary). Although some words, especially in old legal language, contain some examples of an inverted word order than seems more Romantic than Germanic. Some of these are common words, such as “heir apparent” and “court martial” (there are many, many more but these are just a couple examples).

I hope this helped a little bit. Once again: I’m no linguist, but I have researched the similarities between Dutch and English before. It was interesting approaching it from this angle. It helped me to fully grasp the reasons why English seems so different from Dutch and German despite being part of the same language family. Overall a very interesting question to answer.

Some sources I consulted: “The Transmission of Anglo-Norman” by Richard Ingham (proquest), “A History of the English Language” by Albert C. Baugh and Thomas Cable, and many webpages and small articles, including Encyclopedia Britannica, Wikipedia and Google Scholar.