I'm reasonably new to all this, and I have already checked for previous answers but none of them seem to fit with my GParted analysis (below), as other people's results don't really look anything like mine... Moreover, when GParted doesn't seem to allow me to resize anything by the dragging process recommended in other answers.
Essentially, my Ubuntu root hard disk (partition) is only 30GB, and I really need more space to be able to install some new software.
As you can see from the screenshot below, I have 900GB on on my Windows partition; this is completely unused, and there is nothing saved on there.
Would someone be able to briefly explain the simplest way I can transfer some of this hard disk space to my Ubuntu partition?
Many thanks in advance!