Yes, Trump really believes that climate change is a Chinese hoax, because he has mentioned it several times in his speeches. In addition, Trump's proposed policies are not in line with someone who truly believes in climate change, so it is more likely that he does not truly believe it. Rightfully or wrongfully, Trump tends to blame American problems on the Chinese, so he blames climate change on them, too.
It is difficult to determine what Trump really believes. He changes his mind constantly and seems to say whatever is convenient at the moment. It seems silly for anyone to claim climate change is a Chinese hoax and one might hope that no presidential candidate would make such a ludicrous claim and believe it. However, it is very possible that Trump does believe it. More likely, however, is that Trump has no real core beliefs except that he needs to say and do whatever benefits himself at the moment. Period.
The problem with nailing down a Donald Trump position is that he will consistently deny that he has that position, even after he just said it. Therefore, we don't really know WHAT Donald Trump believes. All that matters to him is that SAYING he believes it will get him the kind of votes that he's looking for.
No, Trump does not really believe that climate change is a Chinese hoax because he does not really believe in anything. If having a belief helps his business, he will believe it. If climate change will help him get rich, he will want more of it. He stands for nothing.