1. Well, if you could prove with eye witness that he agreed to sell the proeprty to you in consideration of certain sum of money towards which you paid the said sum of money , the suit of SP lies.
2. Do note to file the suit you have to take plea of sale agreement and not of mortgage.
3.Hence do not refer audio recording which speaks of mortgage and not of sale.
4. Do seek injunction so he may not sell the proeprty to frustrate your claim.