Can't create more than 4 primary partitions.

@[deleted] @algent Hey guys-good news
With the help of mfleetwo from GParted forum I figure out how to manage this drive, here is a link:
http://gparted-forum.surf4.info/viewtopic.php?id=17824
But now I have yet another problem-now I can't install the bootloader on the HDD, where Solus is...it only gives me the ability to install bootloader on the HDD of W10. I don't think that would be a good idea-for more info please check the link to GParted forum.
Also I saw somewhat a similar problem here on this forum(I can't to install Bootloader in my partition...), but from what I can see by @JoshStrobl it's because either 1-they are on legacy mode(I am sure I am using UEFI, because following the instructions I get an image of Solus logo and then I go into the Live OS, instead of me getting only plain text like in old BIOS) or 2-my HDD is not a GPT but a MBR(well quite the opposite-HDD2 where Solus is is GPT, while HDD1 where W10 is and where Solus wants it's bootloader is an MBR).
I have posted a link to video in the GParted forum if you wanna see the HDD configuration and partitions as well as the installation process of Solus.
Update-even when I remove HDD1 I can't put bootloader on HDD2:

I followed the instructions, creating 768 MB FAT32 partition with boot and esp flags-now when I boot the PC there is a new boot option:UEFI HDD2. Still the installer is asking me for MBR partition?!

@[deleted] @algent Hey guys: we've made it!
The longest installation of Solus in history xD I'm a little sad this happened on the 71th post and not on 69th, but whatever.
There were 2 big problems, which I learned how to deal with: the first is that you have to prepare everything with GParted and then try to mount, not via Gparted, but via the installer.
The secound big problem was that I followed the instructions on the Solus website, which said that I have to create MBR scheme for BIOS or UEFI...when I re-burned the USB with GPT scheme, everything, just worked I must admit that I confused the BIOS interface with UEFI when booting Solus.
So here we have it-from my testing I don't like the file system so much, but I will get used to it. Solus is very very fast It's booting is like 3 times faster than W10! It's also very lightweight-I can all the needed programs and some games in less than 10GB!
Unfortunately Waterfox and Joplin aren't available in the software center, but I will learn how to install from other things like snap.
All in all everything is fine, exept now I am only booting into Solus xD
How can I make the bootloader check that there is a Windows and give me choice to boot it?
Also when I turn it off and then on my swap partition and many others get unmounted?! Only the home(which is part of root) is mounted automatically...how can I deal with that?
Which is THE virtual machine for Solus(for W10 I consider it to be Oracle VM)
And most importantly I wanna thank you for the help
Still can't belive you wasted 2 days trying to help me :0 :

[deleted] I figured that there must be additional settings and managed to do that
But this terminal commands always require some password and I just can't type-I begin to write it and I can't-the only thing I can do is press enter and abort the command-I experienced such problems in various Linux distros on VMs...so this is from the stupid linux-y things...
I remember I could do something about it, but what is it?
Update: If it is truly that it's for security reasons and you have to just type the password then the command is not working-I write the command...then write the password and enter-there was no text informing what happened or whatever-I am just on new line to type other commands.

dbarron Well it is absolutely possible, but I am still booting automatically in Solus, instead of W10. I have no options to choose from when booting. What should I do next?

Well it still doen't work here is a video of the process:
https://youtu.be/MCuME5H96RA
And here a picture when I click F12 when booting(if that matters somehow)

dbarron So there is something wrong either with the command or again with fucking HDDs, formats and so on.
Let me give you a bunch of information-maybe some of it will be valuable:
I was with W7 and used the free update to W10-as we've seen W10 is on MBR HDD.
Later I added the second HDD-2TB...after long issues it's now where the bootloader of Solus is and it's GPT HDD.
So is there a problem, because;
1) The 2 bootloders are on different HDDs.
2) The different HDDs are differently formated-one is GPT and the other MBR.
3) Even the format of bootloaders are different-Solus is on FAT32, while W10 on NTFS.

dbarron So the question remains-what do I do xD
Simply deleting W10 bootloader will result in unabillity of booting in in my opinion. Because I can't display both OS with 2 bootloaders, I probably would't with just one
Or I should delete it and then run the sudo commands, but what if it fails?!

[deleted] Reinstalling W10 would mean that I will lose all programs-this is just too much work-I prefer to boot from W10 for my father and when I need to use my PC I will boot via F12...
Although are you sure both of them must be only MBR or GPT?
On multiple places there is that list of commands that you mount different bootloaders, then do some commands, from which the final one is update-grub(your favorite xD).
I may be completely wrong, but it sounds logical to me to show the locations of different bootloaders to GRUB manually and tell it to give you choice when you boot(like Solus-dev/sda....; W10-dev/sdb...; if choose bootloader 1-start Solus, if choose bootloader 2-start W10).
https://askubuntu.com/questions/681422/grub-menu-not-showing-with-dual-boot-uefi-mode-installation