你这个时间应该是现在过去时,如果过去时要有过去的时间,比如昨天晚上。
一般过去时:My sister and I did English exercises last evening.
过去进行时:My sister and I were doing English exercisesat this time last evening.
这个句子可以这样表达:My sister and I were doing our homework.
My sister i were doing our homework.
我和我的妹妹在做我们的作业。(过去进行时)