Create a mod java project from a maven built software

Hi, I have a .jar swing software that was built with maven. I can unpack it and and get the classes back (most of them) - but when I try to set it as an intelliJ project I cant fix the errors to compile it.
So basically I need an experienced java programmer that has experience in creating mods - The goal is to make it work as an intellij project and deliver it to me so I can make my required changes.
to avoid none relevant proposals please type human with an exclamation mark at the beginning of the proposal.
Thank you all!