jeoneun haengsa jeone sureul masiji anhayo.

저 means I in a humble/polite way, and 는 is the topic marker.

So 저는 means something like:

• as for me
• I, in this case

In Korean, the topic marker is very common, especially at the start of a sentence.

You could omit 저는 if the subject is obvious from context:

• 행사 전에 술을 마시지 않아요.
  = I don't drink alcohol before an event.

But 저는 makes the sentence clearer and slightly more natural when introducing your own habit or rule.

행사 means event, function, or ceremony, depending on context.

전 means before, and with the location/time particle 에, 전에 means before in the sense of before a time/event.

So:

• 행사 전에 = before the event

This phrase comes before the main action, just like Korean time expressions usually do.

Examples:

• 수업 전에 = before class
• 식사 전에 = before a meal
• 회의 전에 = before the meeting

What you are seeing is:

• 전 = before
• 에 = at/in/on, and in this case it helps mark the time point

Together they are written as 전에.

So 행사 전에 is literally closer to:

• event before-at

but naturally it just means before the event.

Also, 전 is often used as a shortened form of 이전 in everyday grammar patterns like this.

을/를 is the object marker. It marks what the verb acts on.

Here:

• 술 = alcohol / liquor / drinks
• 술을 = alcohol as the object
• 마시다 = to drink

So 술을 마시다 means to drink alcohol.

Because 술 ends in a consonant, it takes 을 rather than 를.

Compare:

• 물을 마셔요 = I drink water
• 커피를 마셔요 = I drink coffee

In Korean, 술 usually means alcohol or alcoholic drinks, not just any beverage.

So this sentence is specifically about not drinking alcohol, not about not drinking anything at all.

If you wanted to say drink beverages more generally, you would use words like:

• 음료 = beverage
• 물 = water
• 차 = tea
• 커피 = coffee

This is the -지 않다 negation pattern, which is a standard way to say do not.

Breakdown:

• 마시다 = to drink
• 마시지 않다 = to not drink
• 마시지 않아요 = polite present tense: do not drink

So:

• 술을 마셔요 = I drink alcohol
• 술을 마시지 않아요 = I do not drink alcohol

This pattern is very common and works with many verbs:

• 가지 않아요 = do not go
• 먹지 않아요 = do not eat
• 하지 않아요 = do not do

Yes. 술을 안 마셔요 is also correct and very common in speech.

There are two very common ways to negate verbs:

1. 안 + verb

   • 술을 안 마셔요
   • more conversational and direct

2. verb-지 않다

   • 술을 마시지 않아요
   • a bit more formal or neutral in style

Both mean essentially the same thing here.
The sentence you were given uses the slightly more textbook-like and formal pattern.

Korean is generally a Subject-Object-Verb language, so the verb usually comes at the end.

This sentence follows that pattern:

• 저는 = topic/subject
• 행사 전에 = time phrase
• 술을 = object
• 마시지 않아요 = verb

So Korean often feels like:

• As for me, before the event, alcohol, do not drink.

That is normal Korean word order.

By itself, it most naturally sounds like a general habit, rule, or personal policy:

• I don't drink alcohol before events.
• I don't drink before an event.

If you wanted to make it clearly about one specific event, context would usually do that, or you might say:

• 그 행사 전에 술을 마시지 않아요. = I don't drink before that event.
• 오늘 행사 전에 술을 마시지 않아요. = I’m not drinking before today’s event.

In Korean, the plain present negative often covers both habitual and near-future intention, depending on context.

마시지 않아요 is polite, non-formal speech.

It is appropriate in many everyday situations:

• speaking politely to someone you don’t know well
• ordinary conversation
• neutral statements

Compare:

• 마시지 않아요 = polite everyday style
• 마시지 않습니다 = more formal
• 안 마셔 = casual/plain, used with close friends or younger people

So this sentence is polite and natural for normal conversation.

A few possibilities:

• 저는 행사 전에 술을 마시지 않아요.
  Standard and clear.

• 저도 행사 전에 술을 마시지 않아요.
  Means I also don’t drink before an event.
  Here 도 means also.

• 저 행사 전에 술을 마시지 않아요
  This is generally not the natural standard form if you mean I as the topic/subject. You normally want 저는 or 제가, unless 저 is part of another phrase.

So if you mean as for me, I don’t drink alcohol before an event, 저는 is the best choice.

Both can mean I, but they do different jobs:

• 저는: topic marker
  Emphasizes as for me...
• 제가: subject marker
  Emphasizes I as the doer, often in contrast or when identifying who does something

In this sentence, 저는 sounds more natural because you are stating a general personal habit or preference.

• 저는 행사 전에 술을 마시지 않아요.
  = As for me, I don’t drink before events.

Using 제가 is possible in some contexts, but it would sound more contrastive, like:

• 저는 아니고, 제가 행사 전에 술을 마시지 않아요 is awkward
• More naturally, 제가 행사 전에 술을 마시지 않아요 might sound like I’m the one who doesn’t drink before the event, depending on context

So for a simple self-description, 저는 is the better fit.