Paradox Of Time & Choice

Time travel has been a dream of people for years. Albert Einstein's theory allows it to happen with the right technology. Brian White will be sent back in time. A problem will arise when he has no memory of his past. He will arrive in the past hundred of thousands of years. He will meet Denisovans, cave pepole, who predate Neanderthals. His encounter will result in the birth of a child, the future will be changes with this birth.
Brian will find he has been transported somehow into the future where he meets John a Deciple of Jesus, and Mary mother of Jesus. He finds himself jumping into the future where he fights in the crusades with King Richare I, Napolean, and rides with a posse chasing the Doolin gang. He has no memory of his past and wonders how he could be moving through time. A glitch in the computer  program takes him into the future.  This could now cause a problem if the technology is used to change the current future.
An ethical person could use it to change the past to benefit their future. This will happen, but the change of futures has a differern outcome than expected. Will it be better or worse?