The "Parts" does not mean that there is a game 1 and 2. the files are separate ヽ(•‿•)ノ
You must download part 1 and part 2, then unzip the (.rar or .zip) at the same time, selecting both at the same time ( ノ・・)ノ
(DX11 and the other one depend on your PC. If one doesn't work, try the other)