I'm quite sure about that

Dialogue 1 Peter : Are you sure air pollution is more dangerous for the children? Jim : Yes, I'm quite sure. It causes the illness for them.
Dialogue 2 Anne : Are you sure all the garbage is easy to destroy? Marry : No, I doubt about it. The garbage like plastics is difficult to destroy
Dialogue 3 Tamrin : Hey, don’t you know that we have a school bus now? Firman : Are you certain? Tamrin : Yes, of course. The headmaster himself told me.
Dialogue 4 Mini : I heard, our classroom will be renovated in the next view days. Nur : Are you sure? Mini : Well, I can’t tell you for sure. I think we should ask our teacher.
Dialogue 5 Jalal : What do you think we should give Arni as her birthday present? Rusli : A doll, I think Jalal : Are you sure? Rusli : Yes, certainly. As far as I know, she likes doll. Jalal : Well, it is possible I suppose, but I doubt it. Rusli : So, what do you think? Jalal : Why don’t we buy her a wristwatch? Rusli : I don’t think so. It’s too expensive. Jalal : You are right, but we can collect the money. Rusli : Still, I doubt it. I’m broke now. I don’t think I can get enough moneywithin this week. Jalal : Well, doubt isn’t going to do anything. I can lend you the money if you want. Rusli : Really? Jalal : Certainly. Rusli : Thank you very much. Jalal : Don’t mention it.