How to add Windows Boot Manager into boot sequence in BIOS?

Hi

After a failed windows update, I am not able to boot my laptop.

Finally, after being passed from one agent to another during some hours today, I was eventually forwarded to a 14th person at Dell, who was the right kind person to help me with my problem. Hurah!

But we could not find a solution.

During the call, I had to delete the Windows Boot Manager that figured in the sequence, and which was not working. And then to add it again.

So far so good.

I added WINDOWS BOOT MANAGER after clicking on $boot (after choosing one of my partitions).

But it then showed up as WINDOWS BOOT MANAG

I tried again Windows Boot Manager

which, again, came up as Windows Boot Manag

Two letters missing... So this is not working, and computer still doesn't boot into OS.

Any idea how to add Windows Boot Manager correctly?

by the way, I found this file bootsector.bak - is this of any use to restore my boot sector??

Would be great to get some help. I am on that issue full time since 3 days now, and can't even do my normal job. 

Thanks a lot!!

Windows version:  10.0.16299.15 Inspiron 3437