Question

Mandarin Tutorial: Idioms and Related Expressions

Answer 1

学而时习之 - practice and (you) learn
而 = and
时 = time
习 = study/practice
之 = particle not used in modern Chinese

不会说"吃"是白痴 = if you don't know how to say "chi," you're an idiot
白痴 = idiot

三人行必有我师 = three men walk/travel, one must be my teacher
行= to walk/advance/progress (this has a lot of meanings)
必 = must
师 = teacher

basically it's saying, that if you encounter three people, at least one of them has something to teach you

Answer 2

\({\bf{Misc:}}\) expressions related to pronunciation

我们说都适合 = we say it properly
适合 = fit/proper

舌尖顶到牙齿上 = press your tongue against your teeth
舌尖 = tongue
顶 = to support
到 = verb complement of 顶
牙齿 = teeth
上 = means up, in this case indicates the direction of action (up against the teeth)

"ri" 只是 "日" 一个字 = "ri" can only be the one character "日"