I installed Ubuntu after trying it out from a USB disk on my laptop. I made a partition for it, so it shares the HDD with windows 10. Given that at the time I did not have a fast internet connection available, I did not install any updates. Nevertheless the OS worked well: Grub would load, and I could choose to load Ubuntu or skip it. If I skipped it, the boot manager that I installed for windows (suggested by the following site. http://www.everydaylinuxuser.com/2015/11/how-to-backup-windows-10-safe-way-with.html) would appear instead and I could choose to start windows. After I got hold of a decent internet connection I installed the updates, and Ubuntu asked to restart. Upon restart,grub disappeared from the booting process. The notebook jumps just directly to the windows boot manager. I have looked around at this forum and come up with the boot repair solution. Given that I am currently here, it evidently failed. However, it provides a report tool which can be to some use to you http://paste.ubuntu.com/14883071/ I have also tried holding down shift while booting, again, to no avail.
I would very much appreciate your help on this matter, given that I am a newcomer to this OS.