Install Debian 10 on a system which have both GPT and MBR

[p.H]

I have no experience with using third-party tools to resize a Windows system partition.
Unmovable files are usually the swap and hibernation files.
You can disable swap file in the advanced system properties, performance, advanced, virtual memory.
You can disable hibernation with the command "powercfg -HIBERNATE OFF".

[LuxGiammi]

Thanks a lot. I've managed to install Debian on my system: I just made sure to force my BIOS to boot everything in Legacy mode and everything went fine. I put / on my 20GB partition on the SSD, /home on the HDD along with 12GB of swap space (which I will need for hibernation).

Thanks a lot for your help.