What's a good exercise to help built top line and neck?
Hill-work and working them long and low. The only guaranteed way of building topline is consistent, correct work, with the horse bringing his hind end underneath himself, therefore lifting his back and allowing him to reach forwards and down into the contact. Then with hill-work, literally working at a walk up and down slight slopes will make a significant change in a short amount of time. (Making sure that you're asking for a decent walk, not just a plonk!)
My horse gets very excited while jumping and try’s to run. Any suggestions on what to do ex. Figure eight bridle different bit etc?
As counter-productive as it sounds, put on more leg! A lot of times with horses that get too excited they end up unbalanced and running on the forehand. The only way to correct this is by encouraging their hind-quarters underneath their bodies. This will also stop your horse from putting in an extra short stride in front of the jump, and also help your horse throw a better jump in general as he's able to use himself more effectively. To teach your horse to accept your leg pressure riding a leg-yield on a circle is a really good exercise, as it will also get him lighter on the fore-hand. Also, try to keep your leg on during downwards transitions, to keep him "together" and teach him that when you close your leg it means he must collect himself up instead of simply running forwards. Then for jumping, with my horse it helped to build loads of spooky jumps, that he backs off a bit more and to allow you to put your leg on him to jump. Also just going over two poles on the grounds/small jumps set 5 strides apart, and then adjusting his stride from 5 to 4 to 6 etc. Normally this makes them really nice and responsive, as well as them starting to "bounce" more instead of just galloping flat-out over the poles