Well, there are all kinds of things that you could do but I wouldn't recommend most of them. What you have is a trail bike and what want is a MX bike. You would be a lot better off buying a MX bike.
You could rebuild the top end using a high compression piston set to get more power from the engine. The down side is that you will need to run at least premium gas and possibly race gas if you take the compression up too far.
Once you get the bike so that it will go faster the suspension will be a problem, so you will need to take the forks and rear shock to a suspension place and have them re-valved. That will probably cost more than you paid for the bike in the first place.
After all is said and done you still have a heavy bike with limited suspension travel.
At 5'6" you are right at the boarder of being the right size for a full size bike. That TT-R230 has a seat height of 34" while a full size MX bike is 38" to 39". There are trick that you can do to lower the full size bike an inch or two.
If you can, I would recommend finding someone who has a 125 Two stroke that will let you ride it a bit. If you want to race MX that would be a great bike.
A Yamaha WR250 might be a good bike for you. High performance engine, full length suspension travel, just a tad shorter than the YZ line. It also has electric start, which you might enjoy.
Before you do anything, I would get the bike you have out on the track and give it a shot.
Rod