The key icons beside 2 of your partitions indicates that they're "locked". Notice that they're mounted (on / and /boot/efi).
To avoid destroying the partition table of the /dev/nvme0n1 "disk", you cannot edit the partition table while any of its partitions is mounted.
To edit the partition table, boot a Live USB and run gparted from there . You cam easily find a Gparted Live USB on the internet.
If your disk is MBR, rather than GPT, you might have to shrink the primary partition (shrink /dev/nvme0n1p4 first).