Hello @malik123 and welcome to our community! We at Wefugees are happy to hear that this platform was helpful to you so far :)
You can get married to your girlfriend in Germany or France. We listed the requirements for Germany in this thread:
If you need information about marriage in France it’s probably best if your fiancé asks the competent registry office about that directly. Or you can get an overview using this website:
Concerning your other question(s):
In short: as a refugee yourself, marrying another refugee does not change your status. That only works if you get married to a citizen of the country that you live in. In other words: neither will you get a prolonged permit for Germany, nor will your girlfriend get a long term residence permit for Germany just by getting married to each other.
What you can do is getting married (either in Germany or France) and live together through family reunion in one of the two countries. As spouses and acknowledged refugees you usually have a right to be united with each other.
You can find information about family reunion in France on this website:
BAMF offers information about that topic for Germany here: