I should've read about installing ubuntu, now I'm facing grub-efi-amd4-signed GRUB Installation failed error

Sometimes we have to be reminded to RTFM!:)

I've been in the exact situation.
Here's how to make an efi partition.

Make a partition ( 250-300 MB) using some method ( I used cfdisk) at the *start* of the disk. ( Sector 2048 -......). Mark it as bootable and format it as efi. If you cannot directly format it as efi then format it as Fat 32 and then mark it as a efi system partition in the installer prompt. Mount this partition as /boot and the rest should be the same.

Some PS:
I currently use arch hence I've mentioned command line tools (cfdisk). You could use gparted and similar tools.
My efi partition is 300MB.

@silverstar I'm doing with live boot since I formatted my windows, gparted says that I have 3 partitions active? And I cannot part anymore

@nothappy erm you were supposed to do all that on a live session. I'm not sure about the specific problem you are facing. I tried to give a generic solution.
I might suggest going through arch wiki for installation on efi system and follow the parts relavent to you.

@dontbeevil that's what I'm trying to do

@rEaL-jAsE the reason I'm getting Ubuntu is to teach, so that I make little extra 💰 I'm following the schools' syllabus and it requires Ubuntu

So I've finally installed it on the cost of all my previous partitions deleted