so right now I have 3 OS installations on my laptop: 2 Windows 10 and 1 Ubuntu.
I first installed my 1º Windows, then Ubuntu and now I installed my 2º Windows 10.
The thing is before I installed the last one, GRUB was fine (the entry menu was working perfect). After the 2º Windows installation there was no change so I ran "boot-repair" on Ubuntu and now the laptop automatically launchs the "Windows boot window" (don't know the exact name).
My question is: how can I recover GRUB and then make the 2 Windows entries work (on GRUB, not on the "windows boot manager")?
(By the way, if you are wondering why I want 2 Windows 10 installations is because I want to separate my private and working installation).