I had installed Ubuntu on my MacBook, but I don’t need it anymore so I was trying to delete the parts of Ubuntu.

When I entered Disk Utility the minus button was greyed out, so I checked some videos and they explained that sometimes you just need to change the format of the partitions and the minus button becomes active, but I didn’t see any change. Then here on Stack Exchange, I saw that someone reboot his Mac and entered Disk Utility from the Recovery, but when I rebooted my Mac a message appeared: GNU GRUB version 2.06 and now can’t see any of my partitions even when I enter to Disk Utility and if I used Opt I only see EFI Boot.

I hope someone could help me, please. Because I’m very concerned and I don’t want to lose my information.