You could say "I didn't go.... (somewhere: e.g. to the beach 海滩)
I didn't know that (我还不知道)
You could ask a rhetorical question "Didn't you say you went to the beach?" 等等
You could also use wasn't rhetorically "Wasn't that the beach you went to?"
Hope that helps!
很简单啊,首先did和was分别是do和is的过去式,
想表达"是"的意思就用相应人称的be, "我是am人" "它是is狗";
想表达某个动作就用do;
如果想要表达一件"正在做"的事,就要be+doing连用。"我在走路I'm walking."