If you connect an HDD/SSD or a USB stick, the Fritz can function as a NAS: You can set it to access the data via FTP, DAV or as a media server:
https://avm.de/service...
https://avm.de/service...
https://avm.de/service...

The Fritzbox also offers a USB remote connection: You can connect an HDD/SSD or a printer and install the virtual Fritz USB app on a PC and then access or print via USB.

https://avm.de/service...

Since it 'bites' with the media server, a printer can also be connected without the app (works with my old laser printer):
https://www.tecchannel.de/a...

Hello there is a guided tutorial if you look at AVM.de!