单句改错：When i got to America, i found my english was different from which i had learned in China.
答案说改which为what, 但是越想我越迷糊。
在后面的这一小句里，which作from的宾语吗？
这句话完整写应该是：i found my english was different from the one which i had learned in China 对吗？那么后面从the one开始不是应该是定语从句吗？我好迷糊，请大神详细指教