In this way self-confidence grows, first from mastering a subject, then from being able to talk about it.这样,你自信心不断增强,先是因为掌握了一门学问,接下来是因为能够就此发表见解。——《新概念英语》
您好,也就是说,这里的“first”和“then”都是作副词吗?