I have a teacher who dives underwater using supplied air. So he was asking me if I could find him a solution on the internet on how could a diver decreases the amount of nitrogen gas getting inside his body? And how could he get rid of it more quickly?
Trimix, Heliox are typically reserved for commercial divers. Assuming your teacher is not a commercial diver, sport diving offers Nitrox systems that increase the amount of oxygen in the gas mix relative to nitrogen. The risk here though is that icreasing oxygen increases the risk of oxygen toxicity at depth, so if your teacher is really interested they should attend a certified Nitrox training course from PADI or the like.
Sport diving also now offers mixed gas closed loop rebreathers that can be programmed to minimize nitrogen content,but this also requires special training because of the oxygen toxicity issue, and decompression schedules.
Lastly if your teacher limits their dive to less than or equal to 20 feet of seawater, no decompression is required according to the latest no decompression dive tables for sport diving.
The infusion of nitrogen into a diver's blood under pressure, and the diffusion of it out of the blood when the pressure reduces, is driven by fundamental characteristics of the human lung and blood (blood's nitrogen capacity, the diffusibility of nitrogen across the surfaces of a lung's alveoli, etc). There's nothing you can do to a diver to change these characteristics (except perhaps by some sort of blood dialysis, which would be impractical and dangerous all on its own).
The solution is external to the diver: breathe something besides nitrogen. Trimix and heliox replace some or all the nitrogen in the gas breathed by the diver with helium. Helium diffuses more rapidly than nitrogen, so although it enters the blood more quickly on descent, it then purges from the blood more quickly on ascent. (The lack of nitrogen narcosis is an additional benefit.)