If Voller had succeeded in going back to 1939 ..

How long would it have taken him to win WW2?

once he'd killed hitler and his upper echelon he would've put his carefully planned program in operation (30years of future knowledge , genius level scientist etc) most likely developing the A bomb earlier enabling him to put a swift end to the war in like 1940/41 (uses it on US who'd surrender). Nazi Germany then rules the world. Then guess he'd most likely set about advancing civilisation, earlier space travel (since thats what he was working on when he left) moon landings in like 1949, moon bases, Mars landing by 1959 etc. As for Hitlers atrocities i don't think Voller wouldve gone there..

As for Indy i think Voller wouldve imprisoned him, got him medical help and kept him in good health in order to pay him a visit every now and then for discussion/argument over what he'd done (its not like voller would have much intellectual conversations with his American Nazi goons). And once Indy realised all was lost he'd become even more depressed than he was in the movie (the slight consolation knowing at least Mutt would live..). maybe at some point he'd escape and steal the dial and team up with his Dad, Sallah, Marcus, Marion and his younger self (providing they were still alive) to somehow try to reverse things, maybe head to Akator to somehow use the Crystal Skull and the flying saucer go back in time lol