“I want to make you happy seeing you smiling makes me happy.

I want to make you happy .Seeing you smiling makes me happy.
加个标点就好了,因为一句话里不能有两个谓语动词,除非有连词.这句话表示“我想让你快乐.看到你的笑脸,我就很幸福开心.”
希望能对您有所帮助!