it’s longer than anything what i have seen.错在哪里?是错在what吗?小弟英文不好,

it’s longer than anything what i have seen.错在哪里?是错在what吗?小弟英文不好,
it’s longer than anything what i have seen.错在哪里?是错在what吗?小弟英文不好,

it’s longer than anything what i have seen.错在哪里?是错在what吗?小弟英文不好,
改为that

It's longer than anything that I have seen.不确定，呵呵~

what 不能当引导词

It’s longer than anything that I have seen.
定语从句，先行词为anything，所以用that引导。
（先行词是不定代词或者先行词被不定代词所修饰时， 关系代词通常只用that。）

it's longer than anything what i had seen . 这句话是在过去式 ， 所以不应该用have , have 是现在进行式。 希望能够帮到你

what 改为 that