1. Explain it simply
呢 (ne) sits at the very end of a declarative sentence.
It adds emphasis or surprise, like saying 'you know' or 'actually' in English.
It often pairs with 还 or 在 for an ongoing situation: 他还在睡觉呢。
呢 does not make a yes/no question — that is 吗. Never use both, and never double 呢.
2. Show examples
他还在睡觉呢。
Tā hái zài shuìjiào ne.
He's still sleeping, you know.
emphasis on an ongoing fact
外面下雨呢！
Wàimiàn xià yǔ ne!
It's raining outside, you know!
呢 at the very end
离现在还有一个多星期呢！
Lí xiànzài hái yǒu yī gè duō xīngqī ne!
Sandhi:Lí xiànzài hái yǒu yí gè duō xīngqī ne!
It's still over a week away, you know!
adds a 'wow' tone
3. Share a tip
Put 呢 at the very end to stress a fact — 他还在睡觉呢 is a statement ('he's still sleeping!'), not a question. Swap in 吗 only when you actually want a yes/no question.