I tried to grow the ext4 partition by shrinking sda4 and then adding the unallocated partition to the ext4 partition, where Ubuntu lives.
The selected partition, sda6 (see image), contains the bios_grub so I need to move that one. GPartEd however, won't let me.
I have "boot repair disk" on a DVD, so I figured if I just 'simply delete' sda6, assign the unallocated space to the ext4 partition and then booting into "boot repair disk" would make everything work like it should.
I need some help in this, because I need the extra space. Nothing has been done yet, I'm at the point the above image depicts.