You want to say something, you have an idea, you translate that idea into English, you look for the correct grammar, you look for the correct vocabulary, maybe even pronunciation, and then finally you say it.
你想說什麼,你有一個想法,你把這個想法翻譯成英語,你尋找正確的文法,你尋找正確的詞彙,甚至發音,最後你說出來。