Guinea Pig Newbie Help!?

[Exhausted]

So im new at owning a guinea pig, and im pretty sure he's not full grown because hes sorta small and i need help to know if im doing the right thing because i have no idea what im doing. So it all started when my bf got me my guinea pig Gelato for valentines day. I had recently moved to a NO dogs allowed home so i had to get rid of my dogs that i was so attached to. I finally convinced my mom to get me another animal and she comprimised on a guinea pig because they look "less rodent like" than most. So my bf got me one, and later i discovered that guinea pig are compared to dogs sometimes so thats good i thought because im great with dogs. Ive had him for almost a week already and he hides everytime i go near the cage but when im in the room i notice he starts popcorning so im guessing hes happy to see me? He doesnt come to me yet when i put my hand on the cage and im lost on how to "potty train" him. Also they say guinea pig nibble on you when they like you but hes starting to bite sorta hard, not drawing blood but it pinches. i give him an orange everyday sometimes twice because i feed him in small slices so he doesnt stretch his mouth. He wont eat bell peppers or any other veggies hes "supposed to love" he has eaten small cubes of celery out of my hand, once. Some people say when you first got them you have to leave them alone for awhile and i found that out later so i blew that. I cant let him loose in my room for "floor time" because my room isnt guinea proofed, however i let him loose in the bathroom and he just sorta sits there or sits next to me or away from me. When i go to pick him up he runs away from me but then sits still so im not chasing him out of the cage, but should i let him come out of the cage on his own? cuz ive sat there for hours and he doesnt come out! I know a guinea pig is not a dog and i know they require alot of patience but i just need some advice because im completely lost if im doing the right thing? Sorry it was soo long but i wanted to include everything/