All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
There is some ambiguity in your question, but if you had bought the bus directly from your friend with a higher price than its actual price on the condition of paying this amount by installments over a fixed period of time without charging you extra money for the delay in payment, then this sale is valid. However, if your friend gave you the price of the bus so that you would give it back to him with interest, then this is Riba (interest and/or usury) and, in this case, both of you should repent; your friend is only entitled to his capital money without any interest.
As regards the house, it appears that you bought it from your friend with a higher price than its actual price without any interest for the delay in repayments, if this is the case, then this sale is valid.
As regards rescheduling the payments in a way that the monthly payments would decrease and the amount of debt would increase, then this is clear Riba and it is not permissible for both of you to enter this contract under any excuse of need or difficulty.
In such a case when it is difficult for you to repay the debts, what Allaah has ordered your creditor to do is to give you respite until you become able to pay off your debt or that he drops from you your entire debt or a part of it, as Allaah Says (what means): {And if someone is in hardship, then [let there be] postponement until [a time of] ease. But if you give [from your right as] charity, then it is better for you, if you only knew.}[Quran 2:280]
Allaah Knows best.