1. Many brushes are shown twice in my brush presets. I already deleted them, but next time they were back. How can I permanently delete it?
2. A few days too many are displayed for the predefined brushes. How can I delete them without deleting all of them in the day? I would like my own tabs. Thanks for the help.

It sounds like you've been doing some editing of brush presets and got into a confusing situation.
Screenshots of the Brush Presets docker and other things would be useful/essential to understand this.

Please go to https://krita-artists.org/ , sign up and sign in and create a new topic describing your problem.
You'll be expected to say which version number of krita you're using and which operating system you're using.
You'll also be asked what actions and changes you've done with the brush presets and be asked to upload screenshots.

It would be useful to provide all that information in your first post.