Questions about my Macbook Pro...?

Ok so I just got a Macbook Pro last week and I love it but I have some questions. When the battery gets low and it tells me to plug in the adaptor and I turn it off while it charges it usually takes about 3 hours or so which seems normal BUT if I stay on it the whole time it's charging it seems like it charges in no time and much faster than when it is turned off. Or it could just seem that way since I'm on the internet so it could seem like time goes by a lot faster and I'm just not paying attention lol. How long should it take to charge while it is turned off compared to the time it takes while it is being used while it charges? Is it okay for me to use it the whole time while it charges or is that bad for the battery? Also if you have a Macbook how long do you usually use it because I feel like I may be using mine too much. There are days where I'll charge it and use it for 7 hours until the battery is low again and then I'll plug it in and use it for pretty long time after that as well. Is that okay? Sorry for all the questions. It's my first laptop and I want to make sure that I'm using it correctly and not doing anything that could harm it. Thank you very much for your help! :)