Push in on the Free wheeling button on the back until it clicks in place. You should be able to push it forward easily then when it is not running. To try to start it again, release the Free wheeling using the lever by the Free Wheeling button.
Your starter clucth shoes springs are missing or are not functioning to pull the starter clutch shoes back to the rest position.
You can also hold in on the decompression lever (little lever on left handle bar) to make it easier to push.
Check your tail light bulb to make sure it is not burned out. It is a dual filament bulb and is wired in as part of the ignition circuit. If it si burned out your engine will die each time you apply the brakes.
Remove your carb and clean it and don't forget the Idle jet. Do a search on Idle jet to find a picture of where it is and how to clean it.
Put in a new spark plug NGKB5HS gapped at .020
Check the oil in the rear final reduction gear. If oil runs out of the access screw it is OK, If you need to add oil use 80-90 wt gear oil.
Use a 50:1 premix or 2.5 ozs of 2 stroke oil to 1 gal of gas.