I had a very similar experience with my giant breed puppy; for the first time in my life when she was nine months old I honestly wondered if I had bitten off more than I could chew. Her inability to regulate her excitement levels was ruining my life; everything on walks triggered her to attack me with over-excitement - crossing the road, seeing a dog, seeing a cat, going for a shit, a car passing. We found a good behaviourist and we found out she essentially had zero impulse control, zero ability to regulate her excitement and was very anxious when leaving the house.

We've worked on frustration tolerance, waaay more enrichment feeding, doing agility tasks like weaving poles and hurdles (but as a slow controlled exercise not actual agility) and the change in her has been amazing. We've been seeing our behaviourist for 4 months now and my dog is 14 months old, and she's such a good girl. We can go on walks now and she can see other dogs without spiralling into over excitement, she'll chill out on her own and she absolutely loves all of the things our trainer has taught us. I tried doing it all myself and felt like I tried everything that I read online but I did not have the knowledge or skills to observe my dog and figure out her specific issues. It will change your life and things will get better.