I am pretty sure this is a common beginner mistake and it is already answered, but i couldn't find anything helpful.
So since this happened to me twice, I would like to know where my mistake is and what i can do to prevent this.
Also it would be awesome if there was a way of fixing this without losing my data.
What happened is, I created another ext4 partition alongside my existing Xubuntu system (consisting of a EFI and a ext4 partition) and then installed Peppermint on it (the first time this happened it was Windows 7, so i don't think the OS matters at all). Both OS worked perfectly fine, but when I decided to delete the new partition (the one with Peppermint), i couldn't boot it any more, instead it would show me a
grub console where I could enter commands. I can still boot from a live Disc tho.
Thank you for helping and being an awesome community allaround. Johannds