De mporis or in English you can't, means that you are incapable of thinking or acting smart. You can't do anything with your life or you don't know what to do with it.
Example 1:
A guy gets late to his appointment, the other guy gets angry with him and says :
-You stupid mothefucker, De mporis at all. RE.
RE is a Greek word that is used when you want to shout at someone or you are angry with them. It's not polite.
Person : Re asshole! I'll kill you! Why did you do this?
Example 2:
person : Where are you Re niko! Long time no see.
Monos sou or in English alone, means that someone is alone in their life even tho they are surrounded by people. It's also used when someone says or does something and nobody relates to it or they just ignore him.
Example 1:
There is a conversation in the room and suddenly on of the guys out of the blue says something that has nothing to do with the conversation. Then one of his friends replies saying : Monos sou
Example 2:
There are people at a camp drinking hot chocolate around the fire. They are discussing about the day and what they did. Suddenly Nura, who haven't said anything in the past hour says : '' I want to burn everything. ''
Chalaka says: Monos sou