I'm a very shy guy and not able to share my feelings with a girl

Dear writer, thank you for writing in. You mentioned you like a girl but are unsure of how to interact with her. Let's focus on what is it that you want to say to her. When she says "What's up?" , What do you feel like saying and what exactly are you afraid of? I think what might be confusing you is that you might be over thinking it. Perhaps you are also concerned with creating a good impression. It might help you relax if you interacted with her just like how you would with a friend. Once you get comfortable enough, then you can always decide when to tell her that you like her. It will help to ask yourself what do you want from the interaction. Do you want to get to know her and let her get to know you? Please do message back to continue our discussion.