You can ask a solicitor to negotiate with your partner for you, either directly or through your partner's solicitor. Your solicitor may still suggest that you try mediation to settle a particular issue between you.
The High Court can deal with Defended or Undefended cases, the County Court can only deal with Undefended cases.
You will have to go to the court on the day of the Decree Nisi/Dissolution of Civil Partnership hearing to verify the information on your Petition.
The Law Society of NI operates a Dispute Resolution Service (DRS). It is not limited to court referred disputes but can be used at any stage of a dispute.