How to restore the grub menu (are things really bad)?

Question

linux

Good evening.
Installed ubuntu next to windows10 yesterday.
The problem was that the grub menu didn't show up.
I started looking for solutions, repeated everything from video to video, in the end, and ubuntu stopped loading.
And instead of it, the following began to appear:

I started looking for a solution, I found a solution (as I thought, a solution): I started
sudo apt-get install lilo
sudo lilo -M /dev/sda mbr
it all in the Try Ununtu mode.
As a result, I got the following:

After displaying the above picture, this appears:

Worn out in general.
I need your help. I don't know what to do anymore.
Please note that I am a teapot in ubuntu, and I ask you to describe each action in more detail (with specific code, if possible).
And here is another screenshot:

Answer 1

mkdir ubuntu
sudo mount /dev/sdb7 ubuntu
sudo mount /dev/sdb2 ubuntu/boot/efi
sudo mount -o bind /dev ubuntu/dev
sudo mount -t proc proc ubuntu/proc
sudo mount -t sysfs sys ubuntu/sys
sudo chroot ubuntu /bin/bash
sudo grub-install /dev/sdb
exit
sudo reboot

But with your lilo, you also lost the gpt superblock, the backup is used (warning in red in the last screenshot). Google how to fix it. First repair, then restore the hornbeam.