Questions & Answers about Вчера мы с новым коллегой дописали чистовик.
How does the prefix до- change the meaning of the verb in дописали?
The prefix до- adds the specific meaning of finishing an action to the very end. While the standard perfective написали just means "wrote" (the action was completed), дописали emphasizes that you finished the remaining part of the writing, bringing the final draft to its limit or completion.
Why does the sentence use мы с новым коллегой ("we with a new colleague") to mean "a new colleague and I"?
This is the standard Russian way to say "X and I". Instead of saying "I and X", Russians usually say "we with X" (мы с X). The pronoun мы (we) includes both the speaker and the person mentioned. Because the subject is conceptually "we", the verb takes the plural form дописали.
Why does коллега end in -ой here?
It is in the instrumental case because it follows the preposition с (with). Even though коллега refers to a male colleague here (as shown by the masculine adjective новым), it is a noun ending in -а, so it declines like a feminine noun. The instrumental ending for -а nouns is -ой.
Is there a trick to remembering the word чистовик (final draft)?