I don't think it's a proper way.不是一个好方法,并不意味方法差,而且老外说话很委婉礼貌,所以用proper(合适的,恰当的)比good 好.
You should have more conversation practice.在这里要意译,不要逐字翻译,have sth more更贴切.do practice 多少有些别扭,因为do exercise才是最适合的搭配.
I'm sorry to hear that you can't join the speech contest.首先要清楚,sorry可以表示遗憾,而不仅仅是对不起.这是个典型的be sorry to do+that后跟从句的复合句型.