Installing Debian 9 ...

Is it like a pre-rant? You reserve the space in case something goes wrong?

@Jilano yeah right 😂 I’m trying to fix fucking grub , and installing archer t4u driver.

@Biggy If you're still having issues with Grub, you could try rEFInd. Who knows, might work!

@Jilano thank you. I’ll try today.
My debian grub doesn’t recognize the windows 10 from separate ssd.

@Biggy Oh, then definitely try rEFInd! http://www.rodsbooks.com/refind/

Every time I had to set up a multi-boot, that's what I used. It usually even scans your disks and finds all the OSs.

Hopefully it'll solve your issue!

PS: If you have a Windows update, it's likely to put the Windows MBR by default again, but that's fairly easy to fix.