my model make my game lag, how can i compressed it ?

Hi, all, sorry i want to ask how can i compress my model in my game, because my model make my game lag. When i only use 5 model, my game not lag, but when i use 10 model, my game lag and can't play anymore because of lag, how can i compressed my model, or how can i make my game not lag when i use many model on it ? my model is in FBX file. Thanks