Any language that uses the latin alphabet has different rules for how pronunciation is derived from or encoded with the letters. e.g. with your example, the le

Any language that uses the latin alphabet has different rules for how pronunciation is derived from or encoded with the letters. e.g. with your example, the letter pair ‘si’ is pronounced differently in Mandarin that it is in English. So it's not surprising that you couldn't write it down properly in pinyin as you don't know how to transcribe Mandarin into pinyin. But Google does. Another example - without knowing how French spelling works there is no way that as an English speaker you could work out how to correctly spell ‘peut’ (can) just from hearing it.