To figure somrthing out from the information avaiable
To tie the knot means to get married. The image is of two people tied together.
This is not an idiom. It means just what it sounds like -- remain together in a group instead of separating.
adds up, makes sense
When someone puts two and two together, they draw an obvious conclusion from what is known.
The sentence is not, because an idiom is usually a phrase. The idiom is "do lunch," which means to have lunch together, usually while discussing business.
It means he gave his opinion on the subject.
"Turn out" is an idiom that means to gather together. There was a large turn out for the town meeting.
It's not an idiom. It means exactly what it looks like.
"Building bridges" is an idiom for bonding, suggesting the creation of connections and closeness between people or groups.
The idiom "apple shiner" means the teacher's pet.
An idiom that means surrender is to "wave the white flag." A closely related idiom is to "throw in the towel" which means to give up."
Yes, "in a pickle" is an idiom. It means to be in a difficult or troublesome situation.