Wanted to invent a machine to help human beings fly.

想发明一种帮助人类飞行的机器。

He hopes to invent a machine that can clean the ocean.

他希望发明一种可以清洁海洋的机器。

If I were an inventor, I would invent a machine to cook all the food I like for me.

我要是一个发明家，我要发明一台机器，为我做所有我喜欢吃的东西。（商量一下吧，可不可以做两个……）