Stay calm
An idiom is something that does not mean what the phrase says literally, so yes. You can't actually laugh your head off.
This is not an idiom - it means exactly what it says. You should stay fit and healthy.
To turn completely around and head back in the direction you came from.
If used as an idiom, it usually means that you are confused about something. The image is of you scratching your head to try to think better.
It could mean a large roll of hair on the back or top of the head, or it could mean a large buttocks or it could just mean a large bread roll.
Keep an idea in ones head to act on it later.
The idiom "keep your head in the clouds" means someone who is unrealistic or impractical in their thinking, often dreaming or imagining things that are not grounded in reality. It suggests that the person is not paying attention to practical matters and is more focused on daydreaming or fantasizing.
It means to remain calm and rational in the middle of a chaotic or confusing situation. The poem "If" by Rudyard Kipling begins: "If you can keep your head when all about you/ are losing theirs and blaming it on you..."
The head person.
An idiom is something that does not mean what the phrase says literally, so yes. You can't actually laugh your head off.
To have a cool head is to have "the ability to stay calm and think clearly in a difficult situation." It is an idiom and does not mean to literally have a cold head, but to be able to make level-headed decisions and remain calm and collected.
This is not an idiom - it means exactly what it says. You should stay fit and healthy.
To keep struggling and not give up.
A level of craziness comparable to that of a bedbug.
"Dive in head first" is to rush into a situation without thinking.
Keep bothering someone.
It is not an idiom, it is fact. A hose can be used for a water level with hundreds of feet between the two points. As long as two bodies of water are connected somehow, they will be at the same level. As an idiom, it would mean a person tends to seek out people they feel are equal or have the same point of view.