Electrical, lights and ignition

All lights in the car flicker randomly ignition does nothing, all lights fully come on when brake pedal is pressed. Turn the key and nothing happens. The car was fine besides the starter not engaging, so I replaced the negative battery cable and that is when all these problems started. I put the original battery cable back on and it is still happening. Before I changed the cable we could bump start the car and it would run fine but not now.