GParted can't drag and drop partition

Question

I just can't drag and drop a partition to the left to increase its size.

I have 2 partitions:

• 1 unallocated 118Go

• 2 ext4 120 Go

And I want to extend the ext2 to all space but can't extend it by drag and drop:

What can I do?

EDIT:

Sorry, I couldn't do it because it was mounted! I thought it's was not mounted because the USB was disappearing from my Gnome File Manager when Gparted was started and the USB drive selected.

I unmounted it, and then could do it!