Pension Transferability Back to French System

I’m not sure about the details but EU laws regulate such things so I don’t think you will have any problem getting credit for retirement payments made to Germany. The question is if you will later get retirement from both France and Germany or if the Germans make a transfer to the French system so you would only deal with one organization. I am posting a good link that covers a lot of things on this subject although I didn’t find the exact answer to your specific question.
https://europa.eu/youreurope/citizens/w … dex_en.htm

As far as I know (but please consult an expert on this), the pension systems are national - thus you will have to accrue and deal with German "Rente" separately from (and in addition to) your home country system.
In any case, if you work here you will have to contribute (like any other employee in Germany - it's compulsory!) and you will be entitled to payouts as per the regulations at the time.

My wife's experience is as per what Beppi has posted; she worked in Germany, Holland and the UK and has state pensions with each of those countries, plus her UK work-based pension.

Thanks for your quick reply !