Hello Lily Susag,
Thank you for posting in Q&A forum.
Can you see takeownership option via Security tab?
If no, can you change Owner of the folder?
If you cannot see takeownership option, neither take the Owner.
You can start to safe mode and check if you can see takeownership option or take the Owner.
After you can take ownership of the folder, you can change the permission of the folder.
If you have any question or concern, please feel free to let us know.
Best Regards,
Daisy Zhou