Hi,
In Visual Studio code, I’ve encountered the following pop-up while practicing;

What do I do?
thanks in advance.
That seems like you haven’t changed the source code editor to be VS Code in your editor preferences. By default it would generate a Visual Studio (not Code) solution.
Edit > Editor Preferences > Source Code to change it.
Then use Tools > Refresh/Generate VS Code Project and you can delete the .sln file in your project.