A few things that I noticed from the video and wanted to share with you (Please don't take this as criticizing, because I do it to)
I know this is your first race, but I feel like these things will help you as you continue.
1. If at all possible, try not to ride behind the 4 strokes in the turns. They tend to slow down a lot, sometimes to a complete stop. One of our advantages is to be able to come into the turn hot, and hammer out of the turn. A lot of them are lazy and rely on their power to get them going again. I noticed you all but rear ended one of them.
2.Hold the throttle just a bit longer. That is a long, fast flowing track. I noticed that you were revving up the engine well, but you were letting off the throttle quite a bit before turns and some jumps. Believe me, I know this is easier said than done. A lot of guys neglect cornering speed, but us 2 stroke guys can take advantage of this.
3. Smooth out the jumps as much as possible. I noticed several times that you were landing on the 2nd hump of the double jumps. Not only does this slow you down, but it usually feel pretty rough went you land too. (Again, trust me I know all too well, lol). You are only missing the end of the jump by a little bit, so either hit is a little harder and clear it or back off a little bit and not bounce off that 2nd hump.
Hope you find this helpful.