Actually, if you're comfortable handling it yourself, that's perfectly fine. all the comments here are already helpful. But if you'd prefer the peace of mind of guaranteed approval, I can assist you and offer a full refund if your visa is rejected. We have done in Australia before.
If you're not sure why your visa was rejected, I recommend applying through a Soft Power category, such as Muay Thai. However, you must register with a gym that has the proper documentation required by DTV. I can give your some advise. DM please 👌🏼