Complements: result, direction and degree (的/地/得)

✗ 他跑的很快。The particle 的 has been used for the complement marker 得. ✓ 他跑得很快。(Tā pǎo de hěn kuài.) — He runs very fast. When "de" comes right AFTER the verb and describes degree or result, it must be 得, never 的. 的 belongs only before a noun, as in 漂亮的衣服 (beautiful clothes).

✗ 她高兴的笑了。The particle 的 has been used for the adverbial marker 地 before the verb 笑. ✓ 她高兴地笑了。(Tā gāoxìng de xiào le.) — She laughed happily. When "de" comes right BEFORE the verb and describes the manner of the action, it must be 地, not 的 — 地 marks how the action is done.

✗ 我写完作业，然后看电视。With no 了 anywhere this reads as an untensed, habitual statement, not a completed event. ✓ 我写完作业了。(Wǒ xiě wán zuòyè le.) — I finished my homework. 了 can sit right after the complement (写完了) or at the end of the clause, but a completed result-complement sentence must not be left with no 了 at all.

✗ 他说汉语得很好。得 has been attached to the object 汉语, not to a verb. ✓ 他说汉语说得很好。(Tā shuō Hànyǔ shuō de hěn hǎo.) — He speaks Chinese very well. 得 can only follow a VERB, so when the verb has an object the verb must be said twice: once with its object (说汉语), once immediately before 得 (说得).

✗ 他走进去教室。The place object 教室 has been pushed outside the compound complement. ✓ 他走进教室来。(Tā zǒu jìn jiàoshì lái.) — He walked into the classroom. A PLACE object must sit BETWEEN the two parts of a compound direction complement: 走 + 进 + 教室 + 来, never after both parts.

The three result complements are not interchangeable. 完 = the whole action finished (写完 finished writing); 懂 = comprehension achieved (听懂 understood); 到 = the goal attained (找到 found). ✗ 我听完了 means "I finished listening", NOT "I understood". ✓ 我听懂了。(Wǒ tīng dǒng le.) — pick the complement that names the actual outcome, not just any completed action.

了 marks that an action happened or a state changed — it does NOT by itself confirm the OUTCOME. 我看了那本书 (Wǒ kàn le nà běn shū) only means "I read that book" — not that it was finished. Only 我看完了那本书。(Wǒ kàn wán le nà běn shū.) confirms completion, because 完 supplies "the whole thing is done". Likewise 我听了 = "I listened", but only 我听懂了 confirms it was understood.