Intellisense-Errors shown in Editor


I’ve recently installed the Visual Studio 2019 Update to the Verison 16.7.12.

Since then I get all Intellisense-Errors displayed in the Editor as errors.

For example the following method is marked as error:

public override async Task<bool> Save()
  return true;

The message says that this method has no await in it, but I have to implement it that way because it comes from an abstract base-class.

How can I disable the intellisense-error in the editor?

Source: Visual Studio Questions