Help needed: Getting rid of Windows on Dual Boot System

Hey guys, when I installed Linux a year ago, I created a Windows / Linux Mint dual boot system, because I thought I would need Windows from time to time.
Guess what, Linux Mint is so great I only entered Windwos like 2 or 3 times, but in the end I don’t need that trash anymore and want to get rid of it.

When I set up the dual boot, I read somehwere to seperate the partitions, so I installed Linux Mint to its own partition as you can see below, maybe this helps for the taks. I have a 1TB Toshiba HDD /dev/sda. I used it as basic file storage under Windows, now under Linux I just annexed it for the same purpose. It has some weird Windwos partitions I don’t know what they are and how do they get there, I only mounted dev/sda4 for storage.

But the evil Windows partition is that 500 GB SSD. As my steam library is expanding a lot, I need space! So how can I get rid of Windows in a safe way? In my boot menu (it’s called “GRUB”, right guys?) I have a couple of entries, 2 partitions are named Windows but only one of them actually boots into it, the other goes into repair mode and then bootloop. I can look those up if they are important.

So, how can I get rid of the Windows stuff, make the boot menu recognize this, while not harming the Linux disk?

That is how the partition schemes of the 3 disks look like:

1000 GB Crucial NVME

/dev/nvme0n1p1	FAT		649 MB		/boot/efi  
/dev/nvme0n1p2	Ext4	41 GB		/root  
/dev/nvme0n1p3	Swap	18 GB  
/dev/nvme0n1p4	Ext4	941 GB		/home

1000 GB Toshiba HDD

/dev/sda1   NTFS	419 MB  Microsoft Windows Recovery Enviornment (System, No Automount)
/dev/sda2   FAT32	315 MB  EFI Sytem (No Automount)  
/dev/sda3   Unkn.	134 MB  Microsoft Reserved (No Automount)  
/dev/sda4   NTFS	981 GB  Basic Data  --> mounted at /media/gigachad/Data
/dev/sda5   NTFS	367 MB  Microsoft Windows Recovery Environment (System, No Automount)  
/dev/sda6   NTFS	18 GB   Microsoft Windows Recovery (System, No Automount) (Push Button Reset)

500 GB Samsung SSD

/dev/sdb1   FAT32   105 MB  EFI System (No Automount)  
/dev/sdb2   Unkn.   17 MB   Microsoft Reserved (No Automount)  
/dev/sdb3   NTFS    499 GB  Basic Data  
/dev/sdb4   NTFS    694 MB  Microsoft Windows Recovery Environment (System, No Automount)  
Free Space 2.1 MB