If it's not detecting the UnityEngine namespace, which happens quite often actually, you can try a Reimport All in unity. I've had some luck by deleting the .csproj files from the unity project, but I recommend making a back up first, as I have also had this completely mess up my unity projects.
Answers
I have a Unity Debugger for VS Code
I use the visual studio automatically pop-up when scripting in Unity. It's prob not vs code sorry
If it's not detecting the UnityEngine namespace, which happens quite often actually, you can try a Reimport All in unity. I've had some luck by deleting the .csproj files from the unity project, but I recommend making a back up first, as I have also had this completely mess up my unity projects.
OK I'll try that