believe that one´s information, opinions or judgements are correct and noy hesitate to express them feely

If someone knows all the answers, they think they know much more than other people.  Google

An expert knows all the answers -- if you ask the right questions. Google

Heck of a way to get dates; act dumb, and pretend he knows all the answers.  Google

know sth very well

He's what they call a "policy wonk"
in political circles, meaning he knows his stuff inside and out.  google

This guy really knows his stuff. google

He knows his stuff and he is correct in what he says.  Google

know every detail of sth

So, practice until you know it inside-out. google

You'll know it's inside-out because it won't roll down the length of the penis easily. google

Also if you've been using a film long enough to know it inside
out you may like to share your tips on exposure, processing or handling.  google

know a lot about a particular subject

It is a labour of love, written by a man who knows
his Alps and knows his onions ! Google

So there you go, take some advice
from a man who certainly knows his onions. Google

Any investment broker who knows his
onions will have something nice to say about that!  Google