This seems to be from the Bridge of Terabithia. It is a sporting reference. In sports they have heats so the sportsman won the first heat (the first round) and the whole thing (shebang is slang for thing or operation). There is also the use of "Not only ... but also ..." here which is a nice high level way of showing emphasis. Best wishes Bob

A heat in the context of a race is a group of people racing at the same time. Larger races are often broken up into heats when the track isn't big enough for everyone to run at the same time. "The whole shebang" is a phrase which just means "The whole thing", so "Not just the first heat but the whole shebang" means they aren't just talking about the first heat, but all of the heats put together.