After my screen mysteriously stopped working properly, I brought my computer to the shop where I bought it and Lenovo replaced my screen successfully without any extra cost (except for the fact that I had to go to other country twice). Well, for some reason, they thought it would be a good idea to format my PC that previously had Windows and Ubuntu, but even if the Ubuntu partitio was there, I couldn’t access. Anyway, I decided that it was a good idea to format Ubuntu, but it was not as straightforward as I would had liked and I read about many different solutions, so I will just write mine and hopefully it will be useful to someone.
Step 1: Create a bootable USB choosing “GPT partition scheme for UEFI”. I used the Ubuntu 16.04.2 LTS amd64 iso.
Step 2: Go to the BIOS screen (press F2 very fast when booting) and go to “Boot”. Boot mode: UEFI. Fast boot: Disabled. USB Boot: Enabled. Go to “Security”. Secure Boot: Disabled.
Step 3: Reboot the computer with the USB plugged in. If you can’t boot from the USB go to the BIOS and on “Boot”, EFI section, move the USB up to be the first one to boot. If not, it might not boot and might boot Windows instead (this happened to me all the time).
Step 4: Install Ubuntu and enjoy.