Grub2 on efi boot does sot work, always boot Windows

English Install/Boot/Login
1

Hello, I installed LEAP 15.1 on a ASUS X55U Laptop. Everything looks fine, but Grub2 is not working. The Laptop always boots to Windows directly.
I tried several times to reinstall grub:

grub2-install /dev/sda

the ouput is

x86_64-efi wird für Ihre Plattform installiert.
GUID Partition Table Header signature is wrong: 0 != 5452415020494645
GUID Partition Table Header signature is wrong: 0 != 5452415020494645
GUID Partition Table Header signature is wrong: 0 != 5452415020494645
GUID Partition Table Header signature is wrong: 0 != 5452415020494645
GUID Partition Table Header signature is wrong: 0 != 5452415020494645
GUID Partition Table Header signature is wrong: 0 != 5452415020494645
installation beendet. Keine Fehler aufgetreten.

but it has no effect. I need some advice. Thanks

2

Did you turn off fast boot in Windows?

Note some hardware UEFI insists on booting Windows check the boot menu in the UEFI/BIOS

3

That is unlikely to be a grub2 problem. It is more likely a UEFI firmware problem. That is to say, your computer is biased toward windows.

4

I have disabled uefi in the BIOS, then config and install grub2 again. Now it works. Thanks

5

Can you still boot Windows?

6

Yes, Windows still boots once selected from the grub menu.