never mess with GRUB!
lesson learnt -.-"

Even more if you use manjaro! If you use manjaro and install Ubintu or whatever and they install they own grub you get a kernel panic and have to live cd and mount manajo grub again... not funny

I use grub-customizer. It's GUI-based (eww GUI). Give it a try.

it seems you took the hard way

Grub on UEFI can be a nightmare.

@liberaldog the thing happened to me! wasted my weekend to save all my data

Grub is pretty straightforward. I think you guys just need a little practice. You have to make sure your kernel boots the right rootfs and init ram disk, if it's wrong, your mismatched kernel modules might cause a kernel panic, or if the init ram disk is named different or in a different location.

UEFI can be a little tricky, but you just have to I stall grub to the EFI System Partition.

And always remember to run grub-mkconfig -o /boot/grub/grub.cfg (or your distro's location) before installing.

@sheeponmeth My main problem was some weird error with grub and incorrectly making my EFI partition

@liberaldog did you not set the ESP code for the partition? I've done that.