Hi
@Dannysoul , screenshot was fine, picture's worth 1,000 words. This all looks promising. I can give a number of options, and it depends on what you want to do, to advise further.
First up, I would advise safeguarding what you have with the Zorin. Your Zorin is on /dev/sda7, as a Logical Partition within your Extended Partition /dev/sda4. It consumes 20 GiB, so you have either added applications and or personal data, which has effectively doubled it in space consumed since you started 12 months ago. True?
How is the Seagate situated? Can you hook it up, then revisit GParted, and on the top right-hand side where it shows /dev/sda, you can hit the drop-down button, it will likely be /dev/sdb, and take a snap of that and show us?
Very broadly, as I see it, you can choose to rationalise your space on the WD, even move Zorin to top of the partition order, at /dev/sda1, if you wish. You can even use the Seagate to put Linux on, as well as using it for backing up of data.
From the looks of the GParted shot, you have MBR partitioning, and given the Acer's age and the Pentium reference, likely BIOS firmware.
You can put more than one Linux into the space freed up by the absence of Windows, do you have any in mind?
Distrowatch is a good spot if you need ideas.
And its page hit ranking page shows what is most often "hit", which presumes downloads of same Distros. Your Zorin uses a GNOME DE (Desktop Environment) and an article on DEs can be found here -
https://renewablepcs.wordpress.com/about-linux/kde-gnome-or-xfce/
So you can see now, that your question here
Now I have two 159 GB partitions which are completely EMPTY!
How can I use them??
... is a little like "How long is a piece of string?"
, but common, and understandable.
So have a think about it, ask any questions, and once we get an idea of where you want to go, we'll make it happen
Oh, and my Timeshift article is here
https://www.linux.org/threads/timeshift-similar-solutions-safeguard-recover-your-linux.15241/ ... and I am thinking the Seagate is a perfect spot to store a snapshot of your whole Zorin, if you wish?
Cheers
Wiz