If you want to trick train the movements, find a trick trainer to help you.
If you want to perform correct Dressage movements, be prepared to work hard for many, MANY years. You must first develop the horses rhythm, suppleness, straightness, balance, strength, contact and engagement before even being able to ride collection, let alone asking for the movements. The movements in Dressage are not the end goal. The end goal, is to develop the horse to the point that it is so balanced and on the aids that it will be able to perform these movements with ease.
Definitely not something you can trick train within a couple of sessions.
I suspect you do not carry a huge amount of knowledge regarding Dressage and its training - if you seriously want to learn, the BEST thing you can do is to find a qualified and proven Dressage coach. Many people fall off the Dressage bandwagon in the early stages when they realise they won't be riding any 'pretty movements' in their first lesson. It is a sport that requires 100% focus, feel, control and rider discipline to achieve any sort of results.
I suspect your 'collection and extensions' are more so a slowed pace, and a sped up pace. Half pass is an advanced movement, not introduced in competition Dressage until medium/advanced levels (4th level in US?), due to the degree of strength, balance and understanding of the aids this movement requires.
You are best to start off with simple off the leg exercises such as leg yield and turn on the forehand, progressing to shoulder in and travers, which will in turn build towards renvers, half pass and pirouettes.