Fix translation errors in README-cn.md file

Corrected two translation errors in README-cn.md file:
- Fixed translation of ''Do 2 or 3 questions regarding linked lists'' from ''关于链表的问题，请提出2或3个'' to ''请先做2或3个关于链表的问题''.
- Fixed translation of ''but how you apply the knowledge'' from ''而是因为你如何应用这些知识'' to ''而是因为你知道如何应用这些知识''.

This correction improves clarity and better aligns with the intended meaning of the original text.