Snap Crackle Pop, my car won't start

This problem is definitely operator error and at 32 years old, I am sorry to have to ask for help. I McGeyvored my battery terminals a couple weeks back, corrosion unchecked left my vehicle stationary. Due honestly to neglect. I had to cut of the connector thingy’s that connect to the battery post’s, and poorly connected them to new post connectors. My car died again yesterday and is sitting at my girlfriends workplace. I cleaned up the exposed wires on the battery wire connecter lines. and reattached them to the battery connector posts. My battery still has power, radio and lights work, when I wiggle the negative post connector, but every time I try to start my car, it makes a popping noise and flash. I know I have poorly abused my good battery. How do I put things back the right way and hopefully save my battery?