Also there's 2 gears on the front of you mean that one which one?
In general terms: the higher numerically gearing you can change on your bike like 18:1 > 20:1, the more your engine can rev up.
Since the derailleur drive sprocket on the crank/freewheel is replaceable and the chain is tensioned by the derailleur, I'd try putting a smaller sprocket on. You may have to shorten the chain by a link and readjust your derailleur's upper spring tension screw or "B" screw.
You have a shifter kit on that bike, so you have the ability to allow your engine to rev as high as you need. Kitted and worked on two strokes will generally lose a bit of their broad rpm power for a narrower, more high strung power range or powerband.
These are old school two strokes, they were copied from 1950's Japanese bicycle assist engines that made all of their power across a rather broad rpm range. not much power, but it had a wide RPM band of useable torque.
The only way I could illustrate this is for you to ride an older, dead stock, two stroke Japanese small displacement motorcycle like an old Yamaha, Suzuki, or Hodaka trail bike. These old motorbike's power came on at a few hundred rpm above Idle and extended up into about 6000~9000 rpm.
Your engine is now 'kitted', you took all that useable, lower RPM power and scrunched it up into a narrow 2K to 3K rpm band that comes on with more power, but if you're out of that 'powerband', your engine bogs, doesn't accelerate well and you have to downshift to bring the engine up to revs to keep that power going.
This is really not a great set up for bicycle gearing, which was designed for human leg power that generally can be expected to have a wide range of torque, you can always stand on the pedals a bit to get a little sprint going before you fish for a lower gear to keep from burning up your legs on a climb.
You want that power back? Go back to the stock engine setup.