@Gryphon00 said:

Please fix it ASAP and keep me informed about the results. this forum is very important to me.

Demanding we fix it will get you nowhere. You can ask for help though. 502 Bad Gateway means it's not running. Try running ./nodebb dev in your NodeBB folder and seeing if it either crashes and supplies an error, or loads as it should.

Also Refer to the documentation, it'll likely be in there. Link to Documentation