Edit:
SOLVED: in case anyone has the same problem, I Solved it by making my skin materials (Face, Tongue, Teeth,…) to Surface Domain, set its shading model to Subsurface profile, Applied a subsurface profile from an Imported metahuman, and above all, made the material TWO SIDED.
Then Enabling Ray-Tracing ( Directx12, Use hardware raytracing,… ) in project setting, solved the problem.