Tell me where I’m going wrong

We have an almost 6 month old pitbull puppy and she is not potty training well. We take her on 2-3 walks a day, one being 30-45 minutes long, and let her in the yard every 35 or so minutes and she will NOT pee or poop on walks. She will get home and pee in the yard. She also pees in the house all the time. I’m talking up to 5 times just in the evening. She rarely poops outsidetoo. She is good about not peeing in her crate and will pee immediately on going outside after being in her crate. After she pees in the house she is at the point now where she takes herself to the door because I always put her outside after sternly saying “no!” After she pees. Tell me, how am I messing up?