OK, I can talk about german.

To say it right away: German isn't completely homogenized, there are variations and even dialects that would be considered their own languages if they hadn't been united in one country.

Case in point: The Netherlands and Northern Belgium, Flanders, have their own language, called Dutch. But Dutch is also still considered to be a part of the so called Lower German dialects, and tbh, as a Northern German who still knows the own dialect (Plattdeutsch) it's far easier to understand Dutch than someone speaking full on Bavarian, that is spoken in Southern Germany. It's still hard sometimes (Lower German, and even Plattdeutsch, again have their own distinct dialects), but it's doable.

With Southern Dialects on the other hand it's different. It's not just that those (the Upper German dialects) followed the so called Phase 2 Consonant Shift, that it has in common with a 3rd dialect group (Central German dialects) and even a Phase 3 shift - they have partially their very own words and an overall very different pronounciation.

The following map is quite good if you remember that a big chunk of the eastern part is in Poland nowadays (most of the bright orange and the yellow + eastwards), but this is how it was until 1945 and even beyond. There are still people living in Poland who identify as German or at least Silesian, but those are only remnants, > 99% of people in Poland identify themselfes as polish, but I digress:

https://www.wissen.de/lexikon/deutsche-mundarten

Let's get some translations before we go deeper into the map:

"Deutsche Mundarten" simply means 'German Dialects'

"Niederdeutsch" means 'Lower German', "Mitteldeutsch" 'Central German' and "Oberdeutsch" 'Upper German'.

The next 2 points are interesting but irrelevant for your question: "Friesisch" is 'Frisian', also a germanic language but not part of the German dialects, "Slawische Sprachinseln" means 'Slavic linguistic enclaves'. The latter are either outside Germany today or the so called Sorbs, a slavic people that only existed in Germany until a whole bunch of them emigrated to the USA.

City names on the map are "München" = 'Munich', "Köln" = 'Cologne', "Braunschweig" = 'Brunswick', the rest is irrelevant or should be recognizable.

If you look at the map now you might see, that it looks quite different from any other map of Germany. That's because it includes also Austria, most of Switzerland, the Netherlands, Luxemburg and parts of Italy, Belgium and France.

This map is nice, because it looks clean and easy. So here's another one:

https://de.wikipedia.org/wiki/Deutsche_Dialekte#/media/File:Deutsche_Dialekte.PNG (Sorry for using Wikipedia, but this map is just great)

Note, that this map not only distinguishes dialects by colours but also by numbers. But, hey! let's get this even further:

https://blogs.uni-siegen.de/dmw-projekt/files/2017/04/Wenker_dorf-drop_2017-02-21.png

Lol, this one is just about Westfälisch (Westfalian), a Plattdeutsch variety of Lower German. "Duorp", "Dörp", "Dorf" etc simply means village, the map shows, which version is in use in which part of Westfalia.

So, as stated above, there is an overabundance of german dialects, one might even say languages in some cases.

Little anecdote: During WW2 my father, a Westfalian, was a child, too young for the official program of evacuation of children from the cities that were in danger of being air raided ("Kinderlandverschickung"), so his mother took him on her own to rural Bavaria. When they had dictation in school it was like a nightmare for him because the teacher would dictate in Bavarian but he was expected to write it down in standard german. Succeed he did not. *g*

The radio really changed it a bit, but movies and especially the TV actually promoted the use of a common standard language even further, also the world wars and the necessity of units from different parts of Germany to communicate with each other, let alone the refugees from Eastern Germany coming to the west after WW2. The written language had already been standardized, now people started to talk more alike each other, and today there's a fear among linguists that many dialects are already on the brink of vanishing.

But even today you can hear very well from where someone is, and southeners, especially Bavarians, can talk with each other in their language without most outsiders ever being able to understand what they are saying.

Try if you can keep the dialects (well, it's mostly more accents) apart:

One guy changing between different dialects: https://www.youtube.com/watch?v=k7a6ak8QggY

Hamburg: https://www.youtube.com/watch?v=gT53-9b_aO0

Plattdeutsch: https://www.youtube.com/watch?v=tcbsqKitvPQ (full on Platt)

For comparison Dutch: https://www.youtube.com/watch?v=aA7-C0scArU

Ruhr area: https://www.youtube.com/watch?v=iyPXM2sg01I (Starts in standard German)

Cologne: https://www.youtube.com/watch?v=TBwtTOV5Z1s&t=19s

Berlin: https://www.youtube.com/watch?v=qWH5YNfAUT4 (the left one has a slight accent, the other one a broader one)

Bavaria: https://www.youtube.com/watch?v=Ffo_wFf7aC8

https://www.youtube.com/watch?v=8GVoRALu15Q

Saxonian: https://www.youtube.com/watch?v=EQUnU3kXbsg

Hessian: https://www.youtube.com/watch?v=FJb0YNecAiQ (For the most part in english. She's from Hamburg originally, but describes Hessian very well)

Swabian: https://www.youtube.com/watch?v=YoL1AfEqa4o (all speaking standard German, except when subtitles appear. A German can hear, that they are from different regions, in part even from which)

Alemannic: https://www.youtube.com/watch?v=dfWlw8PFbr8

That's the german part of the answer, I don't know much about French, sorry, only that people in the Bretagne, the Languedoc and Elsace and Lorraine have pretty distinct accents.