关于not only but also(急，在线等）

一句翻译：我不仅见过毕加索本人，还了解他的人生经历和所有作品。(in the flesh)
答案给的翻译是：I not only seen Picasso in the flesh, but also know a lot about his life experiences and all his art works.
貌似not only seen肯定错，要怎么改？have seen? 那不是前后不一致？
not only but also句型难道前后不需要一致吗？
可是如果not only see不是又很奇怪，明明不该用一般时的
而have known也很奇怪。我觉得have seen与know最顺，可到底要不要前后一致？

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