Fixes and enhancements are welcome, but if you are planning to do a lot of work, it is a good idea to raise an issue first to discuss it. Generally enhancements should follow the goals of the project described in the main README.
If you have found or believe you have found a bug please open a ticket with a precise description. Make sure to avoid disclosing any sensitive information. In particular debug output or logs may contain names, email addresses, secrets or other sensitive information.
Soemtimes it is very helpful to provide an example repository that demonstrates the problem. If you are able to provide a public repository that demonstrates the problem it will make it much easier to debug and can eliminate a great deal of back and forth.
If want to do something that does not fit with the project goals, particually if you want to include information from an outside system, it is probably best to fork the project.