How do i fix my lawn mower?

If the engine is kicking back, it will be :
1 the blade loose ( check it is tight), or
2 the flywheel key sheared ( remove flywheel and replace key), or
3 hydrostatic lock (oil on top of the piston). Take out the spark plug and turn the engine over until no more oil comes out of the plug hole. then refit plug and start engine
1 and 2 are usually caused by hitting a solid object
3 by tipping the machine the wrong way
Good luck

peter
June 2005