[DOCS-REQUEST] - Environment variables overview lack of beginner instructions & 'N8n with tunnel' lack of document to fix error while using n8n

[taothienpeter]

Hi n8n team,
I'm Peter and I'm new to n8n, coding overall. Currently, I encounter a error while deploying my workflows which i have search on your document for fix.

What information is missing?

1. While using the webhook feature on a self-host on local, I encounter an error with 502 gateway timeout. As far as I can see, this is due to tunnel service that messed up. But from there, I do not find a way to fix it since the doc is lacking how that service is running, what It have dependencies, and which file to change to get the tunnel up and running again,...
   For more information, I have posted on the community to ask about this: https://community.n8n.io/t/tunnel-url-return-502/74860?u=taopeter
2. Instruction to change Environment variables is lacking on the page. As far I can understand from the doc are some variables to change, but unfortunately, I do not know how to change/set the variables since there is no instruction on where to find the file, what file to, and how to.

Describe the page/pages you'd like

1. https://docs.n8n.io/hosting/installation/npm/#updating
2. https://docs.n8n.io/hosting/configuration/environment-variables/

Additional context

1. https://community.n8n.io/t/tunnel-url-return-502/74860?u=taopeter [Same link as above]
2. Since I'm not really familiar with coding, 'File-based configuration' section caught my eye. But upon noticing it, I don't really understand how and why we have to use the "_File".