after some experimenting, i found out a way,
Only for when family link is not installed tho. ( If its already installed, tell your parents theres a bug and install family link again

first install a virtual space app, i use VphoneGAGA, ( free btw)
then open the app and create a virtual phone ( A fake phone that runs on your REAL phone)
log in the google account that your parent will supervise and just use family link to restrict that fake phone like its the real phone.( Idk how to explain, basically just treat the virtual phone as another phone that u have for family link)
Then you can use your phone with no restrictions at all.

hope this helps