Spongey brakes trying to fix?

Hello I've been trying to fix my brakes for a while now. While driving home I believed that my brake booster died it became extremely heavy to apply brakes. I have since then replaced a brake booster the master cylinder break. I have flush the brake lines. I pressure flush the brake lines. I replaced the o-ring that attaches to the vacuum hose that goes to the brake booster to the engine. And I still can't get any breaking pressure once I turn on the engine.