If you are getting to close to the jump, you have 2 options: change your track or change your pace to the first jump. The first jump will determine how you second jump in the line will ride.
If you’re crooked or rushing, your horse won’t have the “arc” you need to clear the fence, resulting in him hitting the fence. If you’re under paced, same thing, horse will jump flatter hitting the fence because they don’t have the push from behind to arc over the fence.
If you ride the right pace, come in straight and have him in front of your leg, even if the distance isn’t great, you’ll still get a good jump. This will also help you get the correct amount of strides between the jumps.
Do you set your own lines? It might be that they’re set too short for your horses stride. I would try setting 2 poles 68 feet or so apart and seeing how many strides you get at your horses normal pace then next time, add another stride. Then go back to the normal and then compress. If you got 5 the first time, then tried for 6 and messed up, keep going for the 6 until it gets done, then back to the 5 again. Poles are frustrating but they teach you a lot without having worry about height. I have a love hate relationship with poles and they are very humbling not matter how good a rider you are lol.
Sorry for the novel, good luck!
Put a pole on the ground in front of the jump. This way, the horse will have to jump before. After a while, the horse will learn to jump better.
I hope this helps :)
Count the strides between the fences when walking and then ride those strides