After system Upgrade via Konsole SteamDeck won't boot

Hello,

because of Discord showing a red banner that the Installation is somewhat corrupted I decided to use
pacman -Syu via console.
After i restarted my Steamdeck CachyOS will not boot anymore.

The boot Menu shows me just “Return to UEFI Firmware”

Can anybody help me getting the system booting again without the need to reinstall it completely?
I already tried to reinstall the kernel packages via cachy-croot and
“sudo pacman -Sy linux-cachyos-deckify” via liveusb but all i get after booting into cachyOS is a blackscreen.

Can anybody help me getting the system booting again without the need to reinstall it completely?