thanks for your help @Cerbera, i corrected my geometry and tried to make a UV like what you made, but i got distortions again.
After some unpackings i got this result :
What do you think about this UV ? is it bad to have this many islands for a simple object like this ?
Edit: Yes, it's a bad idea... I can't get it right, i'm going crazy!
Can you send the project so i can look it up?