Why can I no longer change / save my Instagram profile?

For a few weeks and months I have not been able to change anything on my Instagram profile (change biography / profile, make account public, etc.) … Also, other people who I mark on posts no longer see that I have marked them, let alone where. I've tried everything that works and nothing helps (deleted the app, restarted the phone, reinstalled it, contacted support, etc.) Can someone help me? I'm slowly desperate. It really just has to be due to my account. It also doesn't work on Freuden's laptop or cell phone when I log in there. Do you have any ideas?

Go to the Help button in Settings and ask IG for help

I've already done it, nothing helped.

OK