do we realise how much of a pain in the a$$ it would be to traduce an alien language ?

the first head to head , alien to alien conversation will be funny. how can we be sure that they will recognise what is a rock ? do they have a word for it ? hell do they even have a concept of that ? in ancient greec or rome they did not recognise the color blue. do they put the words in a certain order ? do they even use complicated set of sounds ?