sigoto wo sita ato, douryou to nomi ni ikimasu.

The particle を marks the direct object of a transitive verb. Here, 仕事をする literally means “to do work,” so 仕事 is what you’re doing and takes を.

When you say “after doing X,” you use the past tense of the verb plus あと.
• 仕事をする (do work) → 仕事をした (did work)
• 仕事をしたあと means “after having done work.”
Using the dictionary form (するあと) would be ungrammatical; you need the completed action.

Both あと (in hiragana) and 後 (kanji) can mean “after.”
• あと (hiragana) is more conversational and often used in daily speech.
• 後 (kanji) can be more formal or seen in writing.
The pronunciation and meaning are the same; writing in hiragana just feels more casual.

The particle と means “together with” when connecting people or items for a shared action.
• 同僚と飲みに行きます = “I go drinking with colleagues.”
Using に would suggest direction or target (“to colleagues”), and が would mark a subject, which doesn’t fit here.

This is the verb-stem + に + 行く pattern, meaning “go and [verb].”
• Verb stem: 飲み (from 飲む)
• に attaches to the stem to nominalize it into “drinking”
• 行きます adds “go” → “go (somewhere) for drinking”
So 飲みに行きます literally means “go to drink,” emphasizing movement to a location.

No. You must use the masu-stem (飲み) before に行く, not the dictionary form (飲む).
Correct: 飲みに行く
Incorrect: 飲むに行く

Yes. Two common alternatives:

1. 仕事のあと – using の instead of a verb clause, more compact (“after work”).
2. 仕事が終わったあと – literally “after work has finished,” emphasizing completion.
   All convey a similar time frame, though nuance and formality can vary.