Don’t worry nothing is lost. You just need to chroot into your system using live USB and do the swapon. To chroot,
garuda-chroot -a
Should do it but incase it fails (happens when you have ventoy on your usb) you can follow the steps to manually chroot. → How to chroot Garuda Linux this post goes on to reinstall grub you don’t need to do that.
If you so wish you can just remove the fstab entry for swap and everything will go back to normal.
Please remember to do everything from within this chroot terminal only then the changes you make will be reflected in your actual system and not the liveusb.
Moving on if the fstab file info has been taken from the chrooted terminal then yes your fstab file has quite a few errors.
Notably the top 2 lines Nuova partizione ... /etc/fstab : ... have you written this yourself there? Remove them, then the actual swap partition on the last line.
here is my fstab file for comparision,
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a device; this may
# be used with UUID= as a more robust way to name devices that works even if
# disks are added and removed. See fstab(5).
#
# <file system> <mount point> <type> <options> <dump> <pass>
UUID=C49B-DE4E /boot/efi vfat umask=0077 0 2
UUID=6a7bcee6-f3ae-4c03-b6b0-7cb27fb4c8d4 / btrfs subvol=/@,defaults,noatime,compress=zstd,discard=async,ssd 0 0
UUID=6a7bcee6-f3ae-4c03-b6b0-7cb27fb4c8d4 /home btrfs subvol=/@home,defaults,noatime,compress=zstd,discard=async,ssd 0 0
UUID=6a7bcee6-f3ae-4c03-b6b0-7cb27fb4c8d4 /root btrfs subvol=/@root,defaults,noatime,compress=zstd,discard=async,ssd 0 0
UUID=6a7bcee6-f3ae-4c03-b6b0-7cb27fb4c8d4 /srv btrfs subvol=/@srv,defaults,noatime,compress=zstd,discard=async,ssd 0 0
UUID=6a7bcee6-f3ae-4c03-b6b0-7cb27fb4c8d4 /var/cache btrfs subvol=/@cache,defaults,noatime,compress=zstd,discard=async,ssd 0 0
UUID=6a7bcee6-f3ae-4c03-b6b0-7cb27fb4c8d4 /var/log btrfs subvol=/@log,defaults,noatime,compress=zstd,discard=async,ssd 0 0
UUID=6a7bcee6-f3ae-4c03-b6b0-7cb27fb4c8d4 /var/tmp btrfs subvol=/@tmp,defaults,noatime,compress=zstd,discard=async,ssd 0 0
UUID=1b9b6f2d-a19b-4eee-b2bf-6af31dfdf566 swap swap defaults,noatime 0 0
tmpfs /tmp tmpfs defaults,noatime,mode=1777 0 0
as you can see the swap partition has swap not btrfs fstype. Its mounted at swap not /swap. Using /dev/sda4 is fine but please correct the rest. you can follow my fstab as an example and just replace the UUID with your swap partition’s UUID that can be obtained with
lsblk -f