语法：Pierre,then a baker.was...

时间状语，用doing 形式，或having done

Pierre, then a baker, was very interested in music,
played the piano and the organ (played the piano and the organ时态有问题吧?要么改成playing要么played前边加and)
and
became later, haveing given up the bakery, the organist of the city.
==haveing given up the bakery,became later the organist of the city.
主语是Pierre,谓语是became,主宾是organist.

have been done是指已经完成的。过去完成时的被动语态
our homework having been finished 是说我们已经完成了作业，是属于过去完成时的一种
having been done 是属于非谓语动词被动中的完成时一种

非谓语动词 是在句子中充当除谓语以外的句子成分的动词形式叫做非谓语动词。非谓语动词分为三种形式:不定式，动名词，和分词(分词包括现在分词和过去分词)。