Assalaam walaikum,
Brother,
We have protocols for making salat. These rubrics help us to stay focused. To keep ones head in the prayer there are many things you can do. One simple suggestion is to keep your eyes focused on one spot. If you are at home praying make sure the tv is not on etc. It is more powerful to pray at the masjid. The group being stronger than the individual.
Take a moment to get yourself together before you start the prayer. Allow yourself to know that you are fulfilling the covenant with Allah. And with a contrite heart step into the prayer.
Please take the time to learn the ritual of prayer. The physical motions keep us attentive to being in the presence of Allah. And it is ok..we have to rid ourselves of much to be able to perform a salat. Just keep going.
You are asking excellent questions that benefit all of us.
PS: It is the individual who is listening to the whispers of shytan. The shytan has no power; we give him power by not being 100% submissive to Allah. Shytan acknowledges he is powerless. Shytan knows who the Lord is. Shytan is envious of the Love that Allah has for mankind. And shytan will do his best to make sure man does not praise and glorify Allah. Shytan casts doubt in the heart of man.
It is man that carries the impure being in his heart. We have a choice as to what we carry in our hearts. The Love and Fear of Allah or the love of the evil and envious one.