Also, a machine I used today was mounting usb drives but the owner would be set to root, so a non-root user wasn't allowed to write. Fixed it by commenting out the usb-related lines in /etc/fstab. (I don't know why they were there, but probably something left over from when I installed testing from a usb stick a few months ago.)
Hi Selim, I've solved changing permissions on /media/user/ thanks for help! Pol