Progressive tenses

-고 있다 = to be -ing 
-고 있어요 = am/are/is -ing 
-고 있었어요 = was/were -ing 
-고 있을 거에요 = will be -ing 

지금 뭐 하고 있어요? = what are you doing now? 
공보하고 있어요 = I am studying 

지금 뭐 해요? 
공부해요.