How to settle with the landlord if I am unable to make payment as per RDC court order?

You can negotiate directly with the landlord, and if you reach a written settlement, then take the agreement to RDC.

If the landlord accepts, you may do it, no problem, and ask him to request the installment to be registered in court.

Yes, you can but you are in a weak position to negotiate.

Since the order has been passed, you may follow the court procedure in order to make payment.

You can make a request to the judge for the installment payment.