crime does not pay
I translated that literally into polish and got a point. I am not a native speaker though so I do not understand what this idiom actually means. Who can help us? Why use idioms instead of normal sentences?
Correct translation into Polish is: "Przestępstwo nie popłaca.", which basically means that it's not worth to do crime.
Here you have great explanation about idioms: http://www.english-online.org.uk/adv6/idiom1a6.htm
PS. You should move that question to "Angielski z Polskiego". You can do that by editing your post.