Ubuntu won't boot after installation?

Question

System administration

Good afternoon. In general, I'm confused. I bought myself a new laptop, as I understand it with UEFI, installed Windows 8.1 on it, then Ubuntu 16.04, and when the system starts, the Grub window does not appear with the choice of OC, but Windows simply loads by default. Installed Ubuntu as usual, booted from the Live CD first, then installed next to Windows Boot ..., in general, everything is as usual. Tried booting from Live CD and repairing with Boot-repair, doesn't help. Previously, I did not meet with such a situation, it was put on an old laptop without any dances with a tambourine. In general, everything is very blurry on the Internet, I didn’t find my specific case, and everything converges to the fact that you need to use boot-repair. Disabled secure boot and fast boot in Windiws. The most interesting thing is that after all these manipulations, when you press F12 (boot selection menu), there is nothing except Windiws,the screenshot shows the current partitions. What to do then? Try
bcdedit to tell it where to boot from? Or what? boot-info uploaded to mega.