Think of the verb 'get' as meaning 'become', and think of the word 'lost' as an adjective. 'Get lost' and 'be lost' is the same as the difference between 'get tired' and 'be tired', between 'get drunk' and 'be drunk', or between 'get unhappy' and 'be unhappy'. The first is the process and the second is the state. If you say 'We're getting lost' it means that you are in the process of losing your way. If you say 'We are lost' it means that you already have lost your way.

Both of the answers are correct and "to get lost" also has the meaning of the act which resulted in you now being lost. For example "I took the wrong exit and we got lost. Now we are lost" that make sense? It's a very subtle usage difference.

To be lost means that you are lost now...right at this moment. To get lost is a hypothetical version of being lost that usually implies that it will occur in the future. As in, "we will get lost if we take the wrong street". The phrase, "get lost!" that Jaouad refers to is slang and is like an insult.

To be lost: you lost your way Get lost: it has the same meaning like to be lost but it has another pejorative meaning.so when you say to some one get lost it means you do not want to see that person again.

Thanks for the answers, now it´s clear.