Go to BIOS at startup.
reset/power of and on again, press F9 or F10
and then boot properties from upper menu.
F10 to save changes.
In the meantime follow all directions from your system.
// It should be easier, I have now idea how did you figger out out that secureboot and legacy. I need to read what the hell is it ;) But changing of that options works - THANKS a LOT !!