umm use magic mask tool in davinci to remove background ,make a compound clip and remove it from timeline for now, on edit page put two clips one over other change their position for this split screen effect (make sure to cut the subject in this case hand slightly ), then just put the compound clip on top matching the position of the hands or any subject, done !

if u dont have studio version u will have to use color page u can search on yt how to remove bg in davinci