You need to respond to the lawsuit by filing an "Answer" to the complaint. There are answer forms available from the court.
After you file an answer, and before your hearing before the judge, you have the chance to negotiate a settlement. The creditor does not have to negotiate and can go to court to get a judgment against you for the full amount owing, plus costs and interest.
Your negotiating power now comes from having a significant portion of the debt that you can pay in a lump sum to settle. With a judgment, the creditor must work harder to collect what is owed.