How can I pay the debt to Mykolayiv teploenergo without waiting for the executive...?

YES, you can pay the debt before the opening of enforcement proceedings. To do this, you need to find out from Mykolaiv teploenergo the account to which you need to pay the debt.

In the event that you pay the debt before the opening of enforcement proceedings, in accordance with part 9 of Article 27 of the Law on Enforcement Proceedings, the enforcement fee is not charged in the event of the end of enforcement proceedings on the basis of Clause 9 of Part One of Article 39 of this Law, if the decision was performed before the resolution on the opening of executive proceedings was issued.

If Mykolayiv Teploenergo, for some reason, applies to the enforcement service with a demand to open enforcement proceedings, then after providing proof of payment of the debt, the enforcement proceedings will be closed.