Thank you. In that case.
You can’t make someone an administrator on a Windows 11 device from the Microsoft website. The page you’re viewing confirms this clearly: changing a user’s Windows account type must be done on the device itself.
Does this article help you in any way?
https://www.yourwindowsguide.com/2022/04/lost-administrator-rights-in-windows.html
A Windows MVP writes content on the above website, so it is safe. However, do watch out for the ads. It should translate into your Browser language automatically.