difficult training my puppy.

She's half pit/half lab. I'm trying SO hard to get her potty trained. Absolutely not working out for me. And when I do take her out she gets scared because there's a bigger dog next to where we live which that dog does no harm but she gets nervous. Instead pees and poops inside. Plus her biting! That needs to stop....She's 7 weeks old. I need tips, please. 
Thank you