1. Your laptop is fairly old and (most likely) out of warranty, so there's no help from the manufacturer (unless you pay them).
2. It sounds like your system decided to download and install a major software update. Usually, you have to click 'Install now' in the Settings app, but maybe Windows 10 is configured to install updates without user input (i.e. 'outside active hours').
3. When you say you 'rested for a few seconds' - did you close the lid on the laptop? And for how long were you working on the laptop?
4. Have you tried using the power cable instead of the battery? It would seem the battery doesn't work anymore, or needs to be recharged.
5. I know the screen is dim, but can you see anything at all? Even if it's very dim, see if you can actually open Windows. You can only recover your files from inside Windows or by removing the hard-drive and connect it to another computer.