Get a life | You have no life
Solution 1:
"Life" in this context refers to one's "social life". The implication is that the target has no friends, or nothing of note to do with their time.
Solution 2:
"Get a life" and "You have no life" are slightly different in American English usage.
If you say to me, "What are you doing wasting time here? Get a life!" you're probably saying that I should leave and that what I'm doing is bad; I should find something better to do.
You may be trying to insult me by implying that I had nothing useful to do with my time, so I was behaving childishly or bothering you. However, this meaning is usually less about my social life or friends - in fact, you could see someone with their friends, and still say, "Get out of here, guys! Get a life!" Take a look at American usage of "get a life", including examples like:
To those two groups I say, grow up and get a life and stop making mountains out of molehills!
If you say to me, "Wow, you're here? You must have no life," then you're probably judging my social life as well - you're saying that what I'm doing is pretty boring or bad, something I would only do if I didn't have more worthwhile options. Imagine that you saw me playing videogames all day, and said to someone else, "That person has no life."
Or you could say, "You work so hard - you must have no life," and in that context, you're really only saying that I don't have a social life; you're not necessarily saying that my working hard is a good or bad thing.
Again, American usage for "have no life", many about social life like this example:
...you might think that Venus and Serena Williams have no life outside of tennis. You are very wrong...
You also asked about a literal meaning, but since this is an idiom, there isn't really one that makes any sense (I suppose in playing a videogame, you could say to your buddy, "Over there! Get a life!" to actually mean collecting an extra life).
Solution 3:
It may be better to divide the usage of get a life to:
-
Negative connotation:
to get a life: to have a fuller or more interesting and worthwhile existence, which is most often used in the imperative.
Get a life (idiom), an American English idiom and catchphrase, usually intended as a taunt, to intentionally annoy and upset someone by making unkind remarks to them, laughing at them.
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Positive connotation:
- It can also be used as a polite suggestion, to building a healthy social life. One of your friends may tell you, "Don't waste your time like this. Get a life." And you can say in reply, "How do you get a life?" something like:
Making your own introductions is a life-changing force. But how do you channel this bravado into building relationships that last? How do you find friends that will raise the ceiling of your potential rather than criticize you for your passions? How do you meet girls that belong in your world and not just in your bedroom?
These are things that you should think of when you decide to get a life.
Solution 4:
"Get a life" is a somewhat mild euphemism said to someone who is being a pest.
Similar terms might include go away, knock it off, sod off (British English only), or get lost. The literal meaning can be taken analogously as something like "go do something else".
In your native Russian, it is probably somewhere in between уходи and отвяжись.