Can you follow the posts here:
And also:
sudo nano /etc/default/grub
Ensure that The line for GRUB_CMDLINE_LINUX_DEFAULT="" looks like:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash loglevel=3"
Tap ctrl+o to overwrite, then enter to save current configuration, then ctrl+x to exit the editor.
I will continue reviewing the log when I have more time.