As for using “chinese” I prefer to use english to explain it as this stage I am naturally appealing to beginners or just trying to show people who aren’t familiar with Chinese at all how this language works. You will see that I have characters in other places like the idioms and proverbs as that is for actual learners/speakers.

As for the use of 吗 in my example question above, I will double check with a Chinese friend as I have always learned that without the 吗 you are TELLING the person they know where the post office is. I don’t claim to know everything about Chinese as I am not native. Everyone can make mistakes and I always welcome feedback. 三人行必有我师焉 right ?

…… I have since checked with my Chinese friends and it turns out that I am correct in using 吗 here. Without the “ma” you aren’t asking a question. The “ma” is necessary if you want to ASK someone whether or not they know something.

Given that this in “how to learn chinese online” why not use chinese characters as “chinese” is the written language.

Do you know where the post office is ?

你知道邮局在哪儿

There is no need to use 吗.

“Where” or 哪儿 / 哪里 is an interrogative pronoun. You do not need to use any other question forming structure with it.

That is the word order. You could of course use the other way of asking questions in mandarin and avoid the “ma” by saying :