Problem with cranking

What is your question?

First of all my car won't crank and I know it my starter, so I did replace the startet put everything back. Then try to started it and it crank, but it took a very long time to start. I have to step on the gas pedal in order to start the engine. After that check engine light on. Finf out it my crank sensor, so I did replace with the new one. But now it did the same thing, the engine not running smooth and the rpm it not stable. What it the problem can anyone help me please.