about a contract

Good day everyone..l wish to solicit some sound advice regarding a contract which my mother in law entered into. My mother in law is a retired public school teacher and in which let her parcel of lot adjacent to her house to be used as a day care center...the contract as l read said that the daycare can used the lot for a period of 10 years for free..they have no obligation to pay my mother in law any peso and will leave the structure after the 10 yrs contract and my mother in law will even  have to pay the teacher in-charge an amount at her discretion as they leave....so it is already 6 years now that they have been using the lot for free and they have 3 sessions/classes everyday...but the worse thing is that they do not do the upkeep of the soroundings, trash are all over and we are even the one cleaning it , the  teachers and mothers of the kids are very abusive(bastos) they do not respect our property,their kids throw things in our koi ponds which led them to die, and they entered our property with their vehicles like they own it and so  noisy...and the mothers knew well that they get to use the property for free...now our take is...can we stop the people from using our property? can we stop the contract? anyways we do not earn even a peso from them..and my good hearted mother in law is sick and need money for medicine maintenance...so our initial plan is to let them off so that we can let the property be rented or the daycare will pay rent for her medicine...please give us some legal advice since the teacher in charge said that it is in our philippine law that we cannot get rid of the day care center eventhough they are using it for free...so please please..help us with some advice..thank you very much and God bless.