Verbs
得 for how well something is done
得 hooks a comment onto a verb: verb, 得, then how well it was done.
English puts an adverb after the verb, speaks well. Chinese uses 得 to attach the comment, and what follows it is a plain adjective, so 很 comes back. If the verb has an object, it is usually said first and the verb repeated: 他中文说得很好. This is the second of the three characters said de, and it is not interchangeable with 的.
Examples
他中文说得很好tā Zhōngwén shuō de hěn hǎohe speaks Chinese well
你说得太快了nǐ shuō de tài kuài leyou're speaking too fast
我走得很慢wǒ zǒu de hěn mànI walk slowly
你做得对nǐ zuò de duìyou did the right thing
Watch out
The mistake this causes
Writing 的 instead of 得. 的 links a describer to a noun; 得 comments on a verb.