we don't have lunch at home 可以说 we haven't have lunch at home吗？

we don't have lunch at home 这个对

we haven't have lunch at home 如果你想让这个和前一句意思一样 应该是

we haven't had lunch at home

当然不等于了。前一句是我们不再家吃饭，后一句是我们还到目前为止还没有在家吃过饭。前一句是一般现在时，后一句是现在完成时。看来你对时态问题还是没太弄清楚，建议多看看时态方面的书。