Hello again,
Finally it’s working 
thanks for everyone
here what I did exactly
-I exported my static mesh as .fbx object to blender.
-since I have 64 faces I took one of your suggestions to make it with 16 primitives, so each 4 faces make one primitive
-Select faces you want to copy in blender edit mode,
. duplicate them by pressing shift+D
. I really high recommend not to move your mouse now so the collision will be on the faces you’ve just selected
.press enter then press P button and choose selction from the sub-menu.
. repeat for all vertices
. rename those copies with UCX_ prefix
-export that again to Unreal
- now if you go to edit static mesh windows you’ll see something like this
://i.imgur/8U1rpwE.jpg
-I tested it with other static meshes and here is the final result
://i.imgur/xxheeks.jpg
thank you alot