I wonder what happens if im using an external contract not develop by me and the contract is destroyed , does my contract stops working ? in which case t would not be advisible to use someone else contract
Your contract will still run, the problem will start on some of your functions, if some of those functions what intented to interact with an external contract which has been destroyed (has your example), the repercussion for your contract will be on those functions that interact with that external contract, few words: some functions will not work properly, because part of their logic depend on an external contract that someone destroy.
If you have any doubt, please let us know so we can help you!
is there a way around it , other that have a plan b inside the contract , i mean is there a way to stop the contract from being destroyed if is has a other contracts that depend on them , like for example a relationship on a database if one table is related to other you cannot delete a record without deleting its relations first