You'll need to manually do this since EF Core won't load associated properties automatically, but something like the following should work:
var result = context.Begrip .Include(x => x.Categories) .ThenInclude(x => x.category);
Note that Intellisense may not always function on
at the present, but even if it receives a red underlining, the code should still compile.
You should probably map this to a DTO if you're returning this to the view or an API so you don't have to worry about