FreePBX, extension.conf and sip.conf

Some questions about FreePBX interface and file conf that should manage.
I created all the extensions on my server Asterisk through the web interface without editing configuration files. Through the web interface I see all my extensions but if I edit extension.conf file, inside, there aren’t anyone of the extension that I see from the web interface.
I expected to find my extension and actions to be associated. One thing this:

Exten = extension, priority, Command (parameters)

Moreover, inside the sip.conf there aren’t any informations about my extensions and, if I understood how it works, Something should be present inside.

I do not know if this is the cause why my client voip (x-lite) do not connect giving the error below:

Registration error: 404-Not found

Finally, launching the Asterisk CLI with the command “Asterisk -vr” I donìt see anything when my client try to connect and return an error. So, or my client does not reach the Asterisk server that does not even notice of his call (it’s correct) or I wrong parameters used to launch it :confused: