Suspension comes from collection, which comes from lots of hard work, correct training, knowledge and timing from the rider and building of a horse's strength over time.
Some horses naturally have a lot of suspension in their paces, it is bred into them. Many of the warmblood breeds are now being bred for loftier paces. Thoroughbreds, QH's and many other breeds, are bred to move flat to the ground, so getting suspension in their paces is much more dependant on collection and correct work.
Based on watching the first 30 seconds of your video, I have to agree with Spyder. You and your horse are not ready to move to collection and therefore development of suspension in his paces. You should start regular lessons with a proven dressage trainer to begin working on the Training Scale - developing first rhythm, then relaxation, contact, impulsion, straightness and finally collection (suspension comes under this bracket). This is a process that can take months to years depending on your horse's level of training and your knowledge and skill as a rider.
This also applies to your other post regarding extension of the gaits. Extending the gaits is much harder than it looks, a far cry from the backyard riders version of putting leg on and running the horse onto the forehand so it is forced to take longer strides with the front legs. True extensions require a great degree of balance and strength in a horse, which will only come when the horse is working consistently through, and has begun some degree of collected work, allowing it to put more weight over the hind legs, which will give it the pushing power required to extend it's gait and body without losing balance or rhythm.
Nothing in horse training ever comes easy or quickly, be patient, be prepared to put in the hard yards, and you will reap the rewards.