cancellation of contract to a certain land developer

i'm a ofw and once desired to purchased a property.my sister told me that one of her friend work to a certain land developer which i known afterwards. but during the processing of papers i noticed a irregularities and some technical wording to the agreement which very unfair to our part. is there then any chance for me to refund my partial advance payment to a certain land developer? this developer is so wise that they enable us sign a agreement that we never fully understand because of a complicated wordings and legal terms. they collect to us a total amount of 70k pesos without giving us a single official receipt.i really want to disconnect any connection to them and i want to refund my money,is there any way? pls. advice.thanx in advance..