is there good way to teach language if there's no shared language between Teacher and Student

well here is the Question ....

I see alot of people asking for help in learning Another language from other People 

those people have no shared languages with the people they want to have knowledge from them >

so my question how this could be ???

I mean how you can learn language if the teacher can't make information reach you with the language you know ????

hope this is clear >>>

waiting for answer