As much as I'd like to say this was helpful, it wasn't. The most help I got was from the guy who told me how to open the folder.
With that being said, I am nowhere near. The main cause of this is probably me and I blame myself for that. I will be now hoping to get an Ubuntu Server from HostingItAll, and they will be helping me set up NodeBB!
Thank you very much @PitaJ . now it is ok. but i remember that i had same problem two days ago after configure ngnix and config. site was good also i entered some categories and soon suddenly i got above errors. i hope it wont give error again.