It´s a piece of cake
Very easy to do
Hard nut to crack
Difficult to do or understand
Spill the beans
Reveal secret information
Walking on eggshells
Be very careful not to offend or upset someone
Eat like a horse
Eat a lot of food
The big cheese
Very important/influential person
Like two peas in a pod
Very similar in appearance or character
Go bananas
To become very angry or excited