I had a dual booted Windows 10 and Ubuntu 18.04 machine.
Last month I decided to uninstall and reinstall ubuntu due to some reasons. I deleted the disk ubuntu partition entirely and I also deleted grub. But somehow when I restarted my computer I was still seeing the grub console. To get out of that I had to type in exit three times to boot into Windows. I followed a guide and tried installing Ubuntu using Unetbootin but I couldn't. On top of that now I couldn't even boot into Windows. Instead, I got an error which said I corrupted the hard drive. Then I installed Windows 8(with a cd) on my machine to access Windows 10. So now I have Windows 8 and Windows 10 on my machine. During boot, I get the windows bootloader screen with 3 options --> Windows 10, Windows 8, Unetbootin.
Now I want too install Ubuntu 18.04 the right way and uninstall Windows 8 from my pc but keep Windows 10 and Ubuntu 18 in dual-boot. Please help me. I am a complete newbie to Ubuntu and Linux. Thank you very much.