Unfortunately, it’s a known issue that Intellesense struggles with big projects and UE projects are massive because it contains the entire engine codebase as part of the project too. You’ll need to utilize Tomato software’s tool or Jetbrains Resharper C++ tool
Related video on VS & UE setup: Unreal Engine C++ Development Environment Setup Windows 10 - C++ Unreal Engine development with Visual Studio - UE Casts