Obstay
An Obstay is a person who thinks they know everything and will prove it to you by talking about it nonstop.
My brother is an Obstay. He’ll explain how the internet works and then forget how to use his own phone.
My friend is an Obstay. She’ll talk about how to cook for hours and then burn the toast.
My mom is an Obstay. She’ll tell you how to fix everything but breaks her own glasses.