[Help] Shoping Cart

Hi , iam really new in this software but with the videos and my experience in coding i am geting work done and very quickly , but i need some advise ; where can i find the work that is already done and online? Because i was searching for some shopping cart and after some combinations of words i achive to found something like a shoping cart and i didnt know it had been already created...

Sorry for my bad english...

Thanks!