Desperate for urgent help: How to fix Macbook Pro when repair, erase, reinstall do not work

I have similar problem as many before:

Opening my macbook white loading page w apple and bar comes up. It slooooowly loads to half way, then goes black. Charging doesnt help.

In disk utility there are several 'disks'. Repairing OSX didnt work (says I need to reinstall), neither did erase at first. No idea what the other disks etc are that go under it (disk1, OS x Base System)z

Trying to reinstall: every other time only shows "recovery harddrive", that us locked. What to do??

Other times showed OSX but said problem occured reinstalling..

I am without access to my serial nr or apple repair, on island but with intent and scheduled work for next two months. No idea where to reach out or how to get hold of anyone from apple support as I cannot get my serial nr (or backup that is on exterbaö hd back home)...

thanks for any help. Feeling defeated.