Unable to boot efi unknown filesystem type

/boot/efi is empty somehow.

I followed the other steps, but perhaps with that there is no change.

I am afraid I cannot deduce from your post what the current “state of affairs” is on your system.
Please be more descriptive about what the situation is now after you have followed the steps outlined in my previous post.

Also, post the output of the following commands.
(copy the terminal output as text, paste it into your reply, highlight it and press Ctrl-E to format)

sudo parted -l
efibootmgr 
cat /etc/fstab
sudo tree /boot ## you may need to install tree first