Be careful to say " I know"

Don't say "I know" after other's explanation
When you talk with a foriegn friend, please be careful to say "I know".
I know " I know" is a common answer in Chinese when you have listened to an explanation to your question.  
However, "I　know" means you have know the answer before and don't need other to explain to you. So, if you say " I know" , the one who just explained the answer to you would be very unhappy and see it as an insult.
The better phrase you should use is " got you, cheers" or " understand" or " I have got it".
:): :): :):