Hi Rachid @gecko ,
Could be a few things. The first thing to do, is to get rid of possible ‘double Vertices’; Select everything (in Edit Mode) with A and then M > Merge > By Distance.
You should probably also disable the Clamp Overlap, like so:

And to avoid further problems, make sure the Scale is Applied; in Object Mode: CTRL+A > Apply > Scale.
Let us know if that helps.