Boot is full (no space on device)

Boot is 96% full. Maybe that 's the reason I don 't have apps installed and can 't fix errors. What old cores can I remove from it? There is a screenshot

After a reboot the newest kernel should be booted. In your case 5.5.0-3 - you can check the running kernel with uname -a. If the new kernel works without problems, the old ones can be removed. More answers are available on StackOverflow.

How did you install FreedomBox? I would advice against putting /boot on a separate partition if only to avoid this annoyance.

Yes, I see that the latest version of kernel 5.4.0-3, but uname -a shows 4.19.0-3. That 's why I ask which core to remove.
I installed the Friedombox from the image downloaded from the site.