I want someone to remove from pull request reviewers role which is assigned as deffault. Hovewer, I can't go to project or repository settings.
Welcome to the community.
Admin rights give you admin, not "do everything" (which is a terrible terrible security model). You'll need to look at your rights within the project. As an admin, you'll be able to change them.
It looks like you're new here. Sign in or register to get started.