This may help you with intellisense problems:
Also, try update the VSCode package inside of Unity: Window → Package Manager → Search for Visual Studio Code Editor → Press the Update button
Also, this: No suggestions in Vscode
You might also need to do a Reimport-All if you can get into Unity, or else perhaps close Unity and delete the folder inside your project called Library/ScriptAssemblies, which is where Unity keeps the partially-built code (DLLs) for your game. That will trigger Unity to reload it all when you restart.