Not a duplicate of How to extend my root (/) partition?. That example the reporter can see his root partition. I cannot. I want to resize my root partition to make it bigger but when I run gparted the root partition does not appear. In the screenshot below my root is called /dev/sdb1 but that does not appear on gparted. The other ones do however. Also when I boot using a boot disc and type df then the root partition is called cow.
Can anyone help me to solve this please.

Ok So this is my real problem. I cannot seem to allocate more space to my root partition because as @ByteCommander pointed out I need to select that partition from the top right but when I do that it is the only partition on the screen as you can see from my picture below. So how can I move space from one partition to the next if there is none available before or after it?