第二,其次可以用 besides/what's more 代替 secondly 吗?
可以。
Firstly, secondly 表达“排序关系和递进关系”。
besides/what's more 只表达“递进关系”。
例如:
I don't think I am going today. First, I am feeling a bit tired; secondly, I have been there several times before.
我想今天不去了,一则我有点累,二则我去过好几趟了。
《汉英大词典》
可以改为:
I don't think I am going today. First, I am feeling a bit tired; besides, I have been there several times before.
我想今天不去了。首先,我觉得有点累;此外,我以前去过那里好几次。