dog-dog aggression

Hey, first time poster here. I adopted a german shepherd a month back. She is very sweet, and does very well with training at home. She is like 99% perfect, and I really lucked out with her. However, going for walks is stressful. She tugs the entire time, and gets very distracted by squirrels...

I don’t know if I’m just being a paranoid, so I was hoping for some outside perspective (this gonna be long. Sorry in advance). Angus is a southern mutt (APBT, lab, AmStaff, border collie. 20 no, 85lb) who came to me (MA) from Arkansas. Angus had bitten another dog while in foster up north...

I have a 9 month old male boxer, pitt, ridgeback mix (maybe) named Archer. He's 45 lbs. He has grown up with my other mutt (River) who was fairly aggressive towards him when I first brought Archer home. So my problem that I am hoping y'all can help me fix is that when we go to the dog park...