同学你好，该知识点来自沪江网校《新概念英语2、3、4册连读【双11专享班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~
ever since是副词短语，意思是“打…以后一直”
I simply gave in to him, and I've regretted it ever since.
我就向他屈服了，从那以后我一直后悔。
A few years ago I was asked by a publisher to consider writing a novel, and the idea has been in cold storage ever since.
几年前，一位出版商要我考虑写一部小说，但之后这事就搁置下来了。

had done是过去完成时，强调动作持续到过去的某个时间。这里因为Hans定居的事儿，是发生在奶奶给“我”讲故事之前，而不是到现在，所以不用现在完成时。

可以在这里复习一下现在完成时和过去完成时的区别
https://www.hjenglish.com/new/p939696/

祝同学学习进步~