here is a thread from yesterday with the same issue - you’d need to follow it to the therein linked method do delete a bigger video file to free up space - Fairphone shuts down after entering pin and goes into recovery mode
if your phone is bootloader-unlocked you might have an easier time booting twrp (temporarily) for a GUI method. The user in the thread above had a bootloader-locked device so didn’t have that option available.
I guess you’d need to switch back to the b slot after deletion to be able to boot, let’s see.
(“no disk space left” issues increased in frequency the last week in this forum, I wonder why?)