答:as soon as 表示一···就···,过去时用法:As soon as +主语+动词过去式+宾语+,+主语+动词过去式+宾语
例:As soon as we found this out, we closed the ward.
我们一发现此事就关闭了病房。
after表示一件事在另一件事之后,用法有两种,意思一样:
After +主语+动词过去式+宾语+,+主语+动词过去式+宾语
例:After we found this out, we closed the ward.
发现此事后,我们关闭了病房。
2.主语+动词过去式+宾语+after+主语+动词过去式+宾语
例:We closed the ward after we found this out.
发现此事后,我们关闭了病房。
完成时则是把以上句式中的动词过去式改为have/has been done。
最后说明,after不仅仅用于过去时,后面也可接名词。a wonderful meal 其实是having a wonderful meal 的省略形式,这可以解释楼主的问题。
而楼主的另一个问题this was done不是过去完成时,而是一般过去式的被动语态,相关知识楼主可以查阅一下。