Prevent Texture from being deformed

Hello blenderartists!
I´m using Blender a while ago (newbie) and are doing my first “big” project.
I have an animation with a mesh getting deformed by a boolean object. The mesh is complex, so I can´t use the generated UVs and had to do them myself. I now want the texture using the UV map NOT to deform when the mesh deforms, kinda like stretch the texture/UV instead of deforming it.

Like I said, I´m kind of new to Blender and just watched tutorials yet, so would be cool if you could help me! :o

Thanks a lot