Please tell me it gets better?

I have a 4 month old mini schnauzer who is driving me absolutely mental and I honestly feel like giving up and rehoming him. Every single walk he is pulling to the extreme, like my hands are seizing up by the end of it and he is way too overstimulated on walks so will not ever poop/pee on walks either.

I take him leashed into the backyard to go potty in the same spot but he is suddenly now to overstimulated and distracted and just sniffs/digs or chews leaves and sticks and does not go, then comes into the house and goes inside. When we go outside to potty he is on a short leash and I do not allow him to wander. He gets huge praise and treats every single time he does outside and it’s been this way since we got him at 8 weeks old. Before, he would go reliably outside, within a minute or two. Now, when he realizes he can’t wander and play he eventually just either sits down and stares at me or sits and listens to everything happening outside and will not go. He barks at absolutely everyone and everything as well. Losing my mind. Please give me your tips!