Hello varsay98,
What you are experiencing is expected behavior if your device has restrictions enabled. You will need to work with the devices administrator or remove the restrictions yourself as outlined here: Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support
"Set Content & Privacy Restrictions
- Go to Settings and tap Screen Time.
- Tap Turn on Screen Time, then tap it again. Choose "This is My [Device]" or "This is My Child's [Device]."
- If you're the parent or guardian of your device and want to prevent another family member from changing your settings, tap Use Screen Time Passcode to create a passcode, then re-enter the passcode to confirm. After you confirm your passcode you'll be asked to enter your Apple ID and password. This can be used to reset your Screen Time passcode if you forget it.
- If you're setting up Screen Time on your child's device, follow the prompts until you get to Screen Time Passcode and enter a passcode. Re-enter the passcode to confirm. After you confirm your passcode you'll be asked to enter your Apple ID and password. This can be used to reset your Screen Time passcode if you forget it.
- Tap Content & Privacy Restrictions. If asked, enter your passcode, then turn on Content & Privacy Restrictions."
Regards.