We're going to visit the Great Wall last week.错在哪里

你的时态前后矛盾啊be going to 是将来时 而后面的时间状语却是last weeklast week是过去时的时间状语
这句话可以改成将来时态的：We're going to visit the Great Wall next week.
或者用一般过去时来叙述：We visited the Great Wall last week.
希望可以帮到你