You wrote, Write down that person's name, and declare, "In the Name of the Lord Jesus, I break the power of the devil off Mr John, and i claim his deliverance and salvation." You will be amazed that as simple as that prayer is, you will get the desired result.

That's ridiculous. It doesn't work that way. If that works then why are the vast majority of people unsaved?

(Matthew 7:13-14 NIV) "Enter through the narrow gate. For wide is the gate and broad is the road that leads to destruction, and many enter through it. {14} But small is the gate and narrow the road that leads to life, and only a few find it.

Praying for the salvation of another person is a worthless exercise. You can and should share the gospel with them but they need to accept of their own free will. When you pray for the salvation of another you're essentially asking God to change their free will so they can accept Christ of their own free will. It doesn't make sense.