Maybe you asked: “When do I have to put a comma in a German sentence?” 
Okay, there are some basic rules:
- A comma is put between two main sentences (Hauptsätze): Ich trinke heute ein Bier, meine Frau trinkt einen Wein.
- It’s also put between a main sentence and a subordinate clause (Nebensatz): Ich schlafe viel, weil ich müde bin.
- We also put a comma in enumerations: Ich trinke Bier, Wein, Cola, Wasser und Tee.
- You have to put a comma when you add additional information at the end of a sentence: Ich mag Bier, aber am liebsten deutsches Bier.
Okay, those are the basics 
But there are many other rules. Here you can find more detailed information.
