Yeah it's a little hard to hear. Darren is correct, 'knock over' generally means a robbery. But from the context here, they appear to be using it the same way one normally would use 'push over'. In other words, it will be easy.

Yes, in American slang "knock over" and "to do a hit"...on a business place both mean to rob that place e.g. to rob a bank 🏦. "A safe" is actually....a strong kind of cabinet (made of steel/ metal alloys) with a complex lock, used for the storage of valuables such as money, gold, diamonds, important documents. You can find them at people's homes or at business places. So, "hitting a safe" is actually referring to...robbing a specific location which has "a safe" within its walls. (This is assuming I'm hearing the audio clearly, it's a little difficult to make out).