Hi @YarPav1!
It looks like an LOD version imported from Blender or Unreal doing a tris reduction.
When you Import the fbx into Unreal, did you unchecked the skeletal mesh?
Because it could be the “Reduction Settings of Static Meshes”
Also, did you try the same model in a new project? because if in a new project it looks ok, could be the render settings from your actual Unreal Project.