Managing Firewall Rules and Change requests

Hello Reddit friends,

I am seeking for some advice on firewall change management. At the moment we don't have service desk system in place. Firewall change requests are received via email. Therefore, for the moment I have decided to work on developing a process until management acquires the suitable product.

I'm curious to know what should we in such case?

How to document the firewall rules?

How to manage and approve the firewall change requests ? What about using form ? Do the requester need to sign the form ?

Is there open source tool that can be used internally with security team ?

I would appreciate any insight or advice on this