So, i searched the whole internet for this problem , and i never found a 1 working solution
after deleting the Unreal engine and updating all the vc. to the latest version and following all the solutions you will get in your mind.
and it didn’t work and i still got the same error when i click build and the “Unreallightmass.exe” starts i get the same error.
and after searching i found a comment on another site i don’t even remember the name of it, but god i thank him so much even my kids are thanking him.
he said just download the “D3DX9_43.dll” in x64 because the windows i have replaced by a x32 version,
and he put that link " d3dx9_43.dll free download | DLL‑files.com "
i just downloaded it replaced it in system32 and yeah it is done and i build my light and everything is fine 
- so just download the file replace it
in the system32 and everything will
work just fine <3