I tried to create swap area but unfortonetly i haven't right to create.
I got the following error "swapon: /swap: swapon failed: Operation not permitted"
Is there any another solution, or i have to discuss this problem via VPS hosting administrators?
Given that the error is "Cannot allocate memory", it is memory issue. You'd have to ask the admins or switch to a different provider - digital ocean has some nice options, btw.
As I, and someone else said above, try limiting the connections.
Also, as I said above, check the version - the current is 0.9.1 and your version is showing 32400 which is 0.3.2.4 iirc. The newer versions may handle memory better.