What are the main decision parts of the bible?

The word 'decision' is used only once in the KJV Bible:

Multitudes, multitudes in the valley of decision: for the day of the LORD is near in the valley of decision (Joel3.14)

The 'decision parts' as you mention, come from the preachers rather than from the Bible.

One Scripture that is used here is Revelation 3.20:

Behold, I stand at the door, and knock: if any man hear my voice, and open the door, I will come in to him, and will sup with him, and he with me.

It is said by the preachers that we may make the decision to open the door of our hearts & let Jesus into our hearts. But this is only opened through repentance, as it says in the previous verse, (be zealous therefore, and repent), and this repentance is a gift from the Lord Jesus. (Acts 5.11; 11.18; 2Timothy 2.25)