Hi Krokokeks,
Welcome to our community! 
That’s IntelliSense. See here:
If it does not work for you, please follow the instruction on this website and make sure all required extensions are installed: https://code.visualstudio.com/docs/other/unity
If the issue persists, please check the console of VS Code (not Unity!). If the .NET Framework 4.7.1 (Developer Pack) is mentioned there, download and install it from the official Microsoft website. Here is the link: https://dotnet.microsoft.com/download/dotnet-framework/net471
I hope this helped.
See also:
- Forum User Guides : How to mark a topic as solved