If sparks are coming from starter not good!! Fix what is sparking. Bad connection or bad or loose wire. May get warm .
Make sure that it is not turning over for more than about 15 seconds and than rest it, if you get it too hot you can burn it up ( the starter).
If hard too start, try starter fuild. Check the gap on plugs, if too far apart hard to start, too close burn too cold. Make sure they are set in right range for the plug etc. .