How do we gargle without it getting into our lungs? also, after we gargle how does that excess liquid that we didnt spit out not get into our lungs?

Gag reflex: Gag reflex prevents anything going down in your upper respiratory tract. Unless you are sedated for some reason including some medications when you take more than allowed doses. By the same token there won't be any excess liquid that you do not spit it out will not go to your lungs because gag reflex will prevent it by causing excessive cough forcing you to throw out whatever is in your mouth.