If a persons body and mind change gradually to a higher form than what existed previously, then this is evolution according to my understanding. Do I have the correct understanding? Is the Watchtower teaching a form of evolution?
Only if we allow them to equivocate about the meaning of the word evolution.
Scientists don't think it terms of 'higher' forms of life. Archaea that live in hydrothermal vents under the ocean are amazingly 'designed' to exploit that environment. They are not 'lower' life forms, just different.
Evolution only cares that an organism is good enough to survive long enough to pass on genes to the next generation. There is no such thing as 'perfection'. What would a 'perfect' human be like? We have so many sub-optimal features in our anatomy and in our genome that can't be fixed without going back to square one. Natural selection has no goal or objective to create a 'perfect' anything. Many life-forms have remained unchanged for billions of years.
The other key point about evolution is that it explains how millions of types of living things arose from a common ancestor. It is about the history of life on earth. The Watchtower reject this truth and so it isn't reasonable to claim that they accept evolution of life.
Sorry I missed the thread and took a while to get back to you.