How can one get rid of imagining a physical image of God Almighty during worship and daily activities, despite trying to divert one's mind by contemplating God's creations?

Allah is too magnificent for any created being to comprehend Him. Whatever image a person conjures in their imagination regarding Allah's essence, Allah is not like that. And what comes to your mind is a whisper from Satan. The cure for this is to seek refuge with Allah from the accursed Satan, and to say: "I believe in Allah, the Most Great," and to divert your mind from such imagination.