My dreams will come true. I'm sure about that. that = my dreams coming true Depending on how you emphasise "will" n the sentence, it can vary the meaning. You should use "that" here, not "it". "I believe it" is a rather lame expression. It sounds like: I know it isn't true, but I still choose to believe it.

When you say "I'm sure", its not as firm as "I believe." When you believe in something, there's no doubt about it. But when you are sure about something, you can believe it, but there is still room for doubt and disbelief. For example, when people say, "I'm not sure." Yes, you can replace "it" with "that." Hope I wasn't confusing! :)

When we say im sure we know something and we belive that it is right or that action is going to happen .we can use i belive it for something that you trust.You can use it 2 for a person for exm.I belive him. That is use for objects when they are away from us for exm on a shopping mall u like something and your say i want That but it is used for object but it is a personal pronouns.

Both fine, just mean differently. As what they mean in Chinese, exactly.