acer aspire switch 10 e sw3-013

i have that tablet and windows doesnt boot. didnt work from the beginning anyway. i am trying to reinstall win 10 with the media creation tool. pls help.
i made a usb-stick with microsoft media creation tool.
win 10 + 64 bit + deutsch.
after a lot of hassle. i figured out how to use the uefi-setup tool.
i changed the boot order with usb-hdd on top and even figured out how to enable f12 boot-mgr.
when i switch to boot-mgr via f12 during boot the usbdrive doesnt show up.
what am i doing wrong?
i can even select the usb drive in uefi tool to make the .efi file bootable. still doesnt show up.
do i have to use rufus?
pls help. that tablet is still like new because it never worked properly