why not find a plumber? add a check valve above pump, so

water won't back flash thru the pump. or increase the size of the pipe (more water will be pump out per minute)or change the exit of the pipe. if the outside water reserver is too small for rainning season, you can temperary find pipe exit outside the house, connect a new pipe to the exit, and let the water flow to your yard. anyway, ask several plumbers, they may have better solution. if the whole street or yard is also flooded, then it is a different problem.