The expression is: Do not teach your grandmother to suck eggs. It means Do not presume to instruct an adept. In the days before toothpaste, flossing and dentures were common, many elders had no teeth. Toothless grannies all knew perfectly well how to suck an egg for nourishment.

The idiom is "Don't teach your grandmother to suck eggs." It already is a sentence. The meaning is that your elders have already learned anything you have, so don't think you're smarter than they are. You don't need another sentence except the one above.

You don;t need eggs for most biscuits and pastries.

This phrase is used to suggest that someone is trying to teach something to someone who already knows it. It generally has a negative connotation as it implies the listener is being patronized or underestimated. It may not be well-received in a conversation, as it can come across as disrespectful.