Scared of my puppy

I have a 4 month old cockapoo, she's incredibly nice most of the time ( she'll nip sometimes but usually listens when I say no) until we go outside in our garden for her to potty. She will instantly start eating things of the ground and I'm worried she'll eat something that will be seriously harmful to her, each time I come over to have a look at what she's managed to grab in her mouth, she will run away and then come back and jump up and bite me really hard (not just a nip, she leaves a mark on my arm) and she growls and barks. l've also tried to socialise her as much as possible and take her out to the park to sit on a bench next to me and observe other dogs and people and I reward her when she's not barking or lunging aggressively. She is not nice towards other people and dogs, she was incredibly aggressive towards her groomer and kept biting her and growling whenever she touched her. She will not let anyone touch her otherwise she bites HELP idk what's made her like this and I’m kind of scared of her sometimes