`nginx` - small, but very powerful and efficient web server

nginx [-t | -T | -s signal | -v]

Options you will use

-t: test the configuration (and the certificates and keys it references)
-T: test and dump the full configuration
-s reload: tell the running master to re-read its configuration
-v / -V: version / build options
-g DIRECTIVES: Global directives on the command line: -g 'daemon off;' keeps nginx in the foreground (containers).
-t: Test the configuration and exit.
-s SIGNAL: Send a signal to the master: reload, stop, quit, reopen.

$ sudo nginx -t && sudo systemctl reload nginx

the only safe order

A reload with a broken configuration keeps the old one running and logs [emerg] to error.log - the change silently did not happen.
proxy_read_timeout defaults to 60s: a slower upstream becomes a 504.

Try nginx in a real terminal Free, in your browser - a real Ubuntu terminal to try it in, with missions that check your work.