Comment 35 for bug 1675079

At this point better to start a thread on Ubuntu forums. https://ubuntuforums.org/forumdisplay.php?f=339
Already many similar questions and answers.

Also from live installer: Please copy & paste link to the Boot-info summary report ( do not post report), the auto fix sometimes can create more issues.
 https://help.ubuntu.com/community/Boot-Repair