even if you can conjugate laisser (let) and pousser (push) without even thinking, still, it doesn't guarantee that it will help you with understanding of a phrase laisser pousser — to grow a beard).
laisser pousser can be translated to English as let it grow, and if you see the phrase in a context you more likely will be able to guess/figure out the correct meaning.
But since, among other languages, we're speaking of Russian here I'll bring another example - шнурки в стакане (shoelaces in the glass). This is from kids slang of course, and even in my time no one seemed to use it but everyone knew the 'true' meaning of the phrase anyway.
And I can't help but link the first episode of the satirical/comedy series for kids Ералаш - "Почему мы так говорим?"/"Why we speak like that?"