I have a bachelor's degree in mathematics with grade 15.5/20 and M1+M2 degrees together 12.2/20. (French system university) (M2 degree in differential geometry and geometric control). I want to apply to a phd program abroad and so I need a scholarship to finance my living expenses , my question is : Is it possible to get accepted to a scholarship with my mentioned master's grades ?
There are two issues: getting admitted and getting funding. The first is easier than the second.
There are a lot of variables here, not just your grades. The world is a big place and you don't indicate where you want to apply. Standards vary for both admissions and funding.
You first need to find a place where an application won't be immediately rejected. You then need to convince someone, or perhaps a committee, that you are a good candidate for success.
The rest of this is probably only valid in US, but, if you can get admitted here, then you can probably get funded as a TA, as most doctoral students are. And letters of recommendation are very important and can negate the issues of a low GPA, provided you can show you are sufficiently knowledgeable in the important subjects.
The competition is very stiff, of course, so your application has to stand out in some areas if it lacks in others.
But the only way to know is to make some applications and see what feedback you get. Depending on all of the factors considered you may have a chance. Don't make assumptions and don't necessarily believe everything you are told by people who aren't making the decisions.
For advice on how doctoral admissions works in various places around the world see: How does the admissions process work for Ph.D. programs in Country X?