That's great, Mate
. 3 things before you go -
1. Enable your firewall. Ctrl-Alt-t is a shortcut to open Terminal. Type in, then enter
It will ask for your password, type it in and enter (there is no movement, security). It will reward you with a message that your firewall is enabled in real time and will also be switched on each time you boot/reboot.
2. Make the acquaintance of Tony George's Timeshift, it is installed already on your Mintie. By default it will set up a hidden folder called .timeshift (note the dot, hides it) in your /home/yourusername folder or partition. It is like Windows Restore but way better. Better, with all the space you have, would be to dedicate a partition on one of the externals. You've used 39GB, so you might make it 60 - 80 - 100GB your choice, it can always be grown later.
3. To make the partition, you can use the GNOME Partition Editor, aka GParted. They had it on your install disk, which you could use for the purpose, but I think Mint still removes it on the way out, but it is in your Repositories.
Top right side of GParted screen allows you to go through the drives, you would identify the drive you want to use for GParted, then Create New and set the size, tell it to use EXT4 for Linux, and label it, say, Timeshift?
See my Tute on Timeshift
here, and ask any questions at the Tute thread.
4. If that F11 method begins to annoy you, we can work with you to get a menu called Grub Menu that will appear at bootup, it will feature Linux Mint on top followed by Advanced Options and then Windows Boot Manager, which is the entry point for Windows. Before we would monkey with that, you would perform a Timeshift snapshot, so that if things headed south for the winter, you could roll back with confidence.
OK that was 4, I lied.
Cheers, enjoy your Linux and
Avagudweegend
Wizard