yes , " You will pass with flying colors " i usually say it to my friend before they go to their exams ^_^

Yes, I do. I need them.

People use slang in their speech all the time and it varies from country to country, some of it may be regional or provincial. Australians use a lot of slang and it varies from state to state. I often say, "no worries/not a problem"

Yes it is. If it is remain in our mind then it automatically come out jus as a slip of tounge. It sound like at an elegance to sentence. Expression can be easily notice while we talk however in wrting we can also notice. Hmmm ya , he is a 'goo boy'.

using slang is a good way for beginner. it gives help to sentence.