1. Explain it simply
Insert 得 (can) or 不 (cannot) between the verb and its result: verb + 得/不 + result.
听得懂 = can understand; 听不懂 = can't understand. 拿得动 / 拿不动 = can / can't lift.
This is about ability or possibility, unlike 完/懂 alone, which just states the result.
2. Show examples
我听得懂中文。
Wǒ tīng de dǒng Zhōngwén.
I can understand Chinese.
得 = can
这个箱子我拿不动。
Zhège xiāngzi wǒ ná bù dòng.
Sandhi:Zhège xiāngzi wǒ ná bú dòng.
I can't lift this box.
不 = cannot
这本书我今天看不完。
Zhè běn shū wǒ jīntiān kàn bù wán.
I can't finish this book today.
看 + 不 + 完
3. Share a tip
For the negative use 不, not 没: say 看不懂 for 'can't understand'. Keep 得 or 不 between the verb and its result.

