resizing an ntfs-partition without any loss of data, while running ubuntu (studio) from a live usb

This is my very first question on askubuntu. I know there are quite a few similar threads hanging around here and there, but most of the answers given have either proven to be too technical, or haven't quite worked for me. So, here's my situation:

I've been running ubuntustudio 16.04 from a live usb-stick for a few days now, since my windows 7 ultimate installation suddenly stopped booting after running an update of my antivirus program. I went with the studio-version 'cause I'm interested in trying the various multimedia production software included. One thing that's been bugging me is whether it lacks any functionality in terms of data-recovery etc. as compared to "normal" ubuntu, so any clarification on this point would be appreciated.

Apart from all that:

I only have one properly working usb-stick available (the one that I'm currently running ubuntustudio live from), so creating multiple live usb:s to boot various tools is not an option (helpful as it might have been).

Neither do I have lots of hard drive space available, so whatever I do, I've got to do it without any backups (unsafe as it may be).

I would like to create a partition to resize my 480GB SSD drive, and there install the ubuntustudio OS that I'm currently running live from my 16 GB usb-stick, so that I can then format my stick and create a live usb installation for Windows 7 to see if I can repair it.

When right-clicking on my SSD's icon, I see under "properties" that I 've got 97.9GB free space, which sound pretty accurate. When viewing the same device in G-Parted, I see one partition with 355.92 GiB of used space and 91.21 GiB of unused space, as well as another 1.84 MiB of unallocated space. I had to quit and reopen GParted a few times to finally get to view this information. Inbetween I tried downloading the latest reportedly stable version of ntfs-3g from here, but then I wasn't really sure what to do with it, so I tried typing sudo apt get install ntfs-3g from within the terminal, instead. The results weren't any better, though, so I went back to my firefox downloads folder, extracted the ntfs-3g archive, right-clicked on the extracted folder, and chose "Open Terminal Here". Then I typed:

./configure
make
sudo make install

and later I added

sudo ntfsfix /dev/sdc1

This seems to have finally done the job, since I'm able to see the partition information in G-Parted.

Next step is to create a Partition in order to install ubuntustudio 16.04
What exactly are the steps?
What file-system should the new partition be based upon and how large should it be? (available unused space is, as mentioned, 91.21GiB, according to GParted).
Can it be done "mouse-wise" or is command-typing necessary?
How safe is it (like, statistically)?

PS My acquaintance with Linux is evidently far from adequate.

PS2 My Windows 7 installation is located on another SSD-Drive, with only 6.07GiB available unused space out of 111.69GiB in total (according to GParted).