When i export a final cut pro soundtracks to soundtrack pro i can make changes i want but when i save my project i lose the connection with final cut pro. I hope that someone can help me Thanks

If you send a Sequence as a whole to STP, it can not send the multitrack project back to FCP. You have to export it as an AIFF first, then import that into FCP. Turn off all tracks except the new Master Mix aiff you just created.