dual boot - Install Windows 10 alongside Ubuntu 18.04

I'm trying to install Windows 10 alongside Ubuntu 18.04 beacuse I want to try some games on my laptop, and then go back to Ubuntu.

I have two USB Flash Drives, one with Windows 10 and the other with Ubuntu 18.04

These are the steps I've done after following some answers here on AskUbuntu.

1) Booted on Live Ubuntu, and shrinked my 1TB HDD into a 500 GB ntfs partition with GParted;

2) Booted on my Windows 10 USB Flash (on UEFI) and installing windows without deleting the partition or formatting it, just by pressing next ( I also tried deleting it and make a new one with Windows but I encounter the same issue);

3) After install, it was directly booting into windows, probably installing other stuff, and this is the annoying part, Windows freeze at "Getting devices ready" or something like this. I forced it to shut down and then .. continuing to step 4;

4) I booted again on my Live Ubuntu USB, and I have installed boot-repair, doing the recommended installation.

5) After installing boot-repair, I restarted my laptop, booted on Ubuntu OS redirecting me to GRUB Boot Loader, I selected Windows everything loaded then I got this error that Windows isn't installed properly and I have to restart and reinstall it.

I really don't know what to do anymore, I deleted the ntfs partition and extended my ext4 partition, everything is normal now, but I really need Windows 10, I also need an answer on how to uninstall it and go back to normal.

This is one of the question I was following but it doesn't work for me

And this is the second question, and I was following the first and the second answer, except doing the mount /boot thing beacuse I didn't know what to do exactly

EDIT : Here's the summary of boot-repair