When Germans want to talk about talking, they don’t use sprechen, they usually use the verb reden.
In German there are lots of expressions for “talking nonsense” so you can choose your favorite!
Examples
Quark reden.
Quatsch reden.
Blödsinn reden.
Unsinn reden.
So, if you want to get someone to STOP talking rubbish (informally), all you have to say to them is:
Red keinen Blödsinn.
I filmed myself.
I filmed myself teaching a group of absolute beginners German - for over 20 hours!