Hi Karsten, @KBfly
I’d be very happy to help you or others fly in France.
Of course you have to speak English or French on the radio. I believe it’s mandatory to file a flight plan to cross the border and to land at an aerodrome that has customs service. (?)
Once that formality is completed you can fly freely in France while respecting the chart.
It’s on this second part that I could help you without limit.
You can largely fly in France without a radio (uncontrolled zones or Class E). It’s fairly easy to avoid zones where the radio is mandatory.
You can take off from an X airfield to go to Y without stating your flight intentions, even on a 600 km trip at 4,000 ft for example. You don’t have to account for yourself as long as you don’t cross Class D or R zones, nor CTRs.
Otherwise, with a minimum of English, if you can receive and read back to the FIS officer a transponder code, a radio frequency and a QNH that unlocks transitions into Class D. (Otherwise you have to go around.) For R zones that depends on the reason for the R, its activity (active or not), and whether you can obtain authorization or not. In general you can easily pass above or below R zones if in doubt.
For Class C with “control”, you need operational English otherwise it’s going to get hot! 
Same for CTRs.
In France 90% of runways are open! Good news.
We could talk for a long time but it’s best to talk about what particularly interests you. Don’t hesitate to ask targeted questions. If you have a project, a route, etc., it will be easy to discuss a concrete plan.
I’m good at cartography, but not at paperwork. I’ve never filed a flight plan in my life… I have a lot to learn on that side! I hope to fly to Italy, Spain and Portugal.
Germany should be easy for me because I’m bilingual 
however I don’t know the local rules! Flight declaration, etc. It will be best to open a separate thread for that.
I’m located between Paris and Brittany. So W - N/W. I fly an ultralight (ULM) with a 912ULS, radio, transponder. Cruise speed 130 km/h at 4,200 rpm, range 800 km. I don’t like to fly faster; if needed a sustained 160 km/h would be possible but it doesn’t appeal to me. (205 Vne) I also do mountain flying (Alps and Pyrenees). With the tent and the gas stove, and the restaurant when there is one.
I remain at your disposal for any questions you may have. We can also talk by phone.
Safe flight,
Daniel.