The mod is written in Java. If you want to start modding it is highly recommended to have experience in writing Java. Other than that, there's the Forge documentation and the Forge Forums for further questions about this subject.
where can I give suggestions on things to add to the mod
this is something I don't think has been recommended before so I think it might be something you haven't thought about
Just write it in the suggestions forum. It should be avaiable for everyone too see/comment.