i have a 7 month puppy who i was hoping to show but i find her under neck quite saggy will it tighten or will it always stay saggy

As she's just a pup I wouldn't worry too much about it - all pups have loose skin. To be on the safe side you could practice hiding it though. I had a zoi with a similar problem, I used to (gently) pull the skin taught under his chin and hide it in my hand, he was a very successful show dog 

Photo of him standing, and a closeup of my handling technique!

thankyou