geu bubuneun jumalmada gongwoneseo sanchaekhaeyo.

In this sentence, 그 literally means that, but in natural English it can often feel like the depending on context.

• 그 부부 = that couple
• In context, it may also be understood as the couple if both speakers already know which couple they mean.

Korean often uses 그 to point to something already mentioned or already known in the conversation.

부부 means a married couple or husband and wife as a pair.

A few useful notes:

• 부부 refers to the two people together as one unit.
• It does not mean just any couple dating each other.
• You do not need a separate plural marker here. Korean often leaves plurality unmarked when it is already clear.

So 그 부부는 means as for that married couple...

는 is the topic particle. It marks 그 부부 as the topic of the sentence: as for that couple...

So:

• 그 부부는 = As for that couple, ...

A learner might compare this with 이/가. Very roughly:

• 는/은: introduces or contrasts the topic
• 이/가: marks the subject more directly, often with a sense of new information or emphasis

In this sentence, 는 sounds very natural because the sentence is simply describing the couple’s usual habit.

주말마다 means every weekend.

Here:

• 주말 = weekend
• 마다 = every, each

So X마다 means every X or each X.

Examples:

• 날마다 = every day
• 주말마다 = every weekend
• 해마다 = every year

This grammar is used when something happens regularly each time that unit occurs.

It is 공원에서 because the park is the place where the action happens.

• 에서 = at/in a place where an action occurs
• 에 = to/at, often for destination, existence, or time

Since 산책해요 is an action, 에서 is the correct particle here:

• 공원에서 산책해요 = walk in the park

Compare:

• 공원에 가요 = go to the park
• 공원에서 산책해요 = take a walk in the park

산책해요 comes from 산책하다, which literally means to take a walk or to go for a walk.

Breakdown:

• 산책 = walk, stroll
• 하다 = to do
• 산책해요 = polite present form of 산책하다

In English, we usually translate it as:

• take a walk
• go for a walk
• sometimes simply walk

It is a little different from 걷다, which means to walk in the basic physical sense of walking.

So:

• 산책하다 = walk for leisure / take a stroll
• 걷다 = walk

Because Korean is normally a subject-topic/object/location + verb language, often described as SOV or more broadly verb-final.

So in this sentence:

• 그 부부는 = as for that couple
• 주말마다 = every weekend
• 공원에서 = in the park
• 산책해요 = take a walk

The verb usually comes at the end, unlike in English.

산책해요 is in the polite, non-formal style, often called the 해요 style.

It is very common in everyday conversation when speaking politely.

Compare:

• 산책해요 = polite everyday speech
• 산책합니다 = more formal
• 산책해 = casual, used with close friends or younger people

So this sentence sounds natural and polite in normal conversation.

Yes, you could, but the nuance changes slightly.

• 그 부부는 ... = As for that couple, ...
• 그 부부가 ... = That couple ... with more direct subject marking, often sounding more focused or specific

In many situations, 는 is more natural for stating a general habit, while 가 may sound like you are identifying exactly who does the action or answering a question like Who walks in the park every weekend?

So both are possible, but 는 fits a neutral descriptive sentence very well.

It is grammatically in the present tense, but the meaning is habitual because of 주말마다.

So it means something like:

• they walk in the park every weekend
• they usually go for a walk in the park on weekends

In Korean, the plain present tense often covers:

• current actions
• general truths
• repeated habits

The phrase 주말마다 makes the habitual meaning clear.

Yes. Korean often omits information that is clear from context.

For example, if everyone already knows who you are talking about, you might hear:

• 주말마다 공원에서 산책해요.

If the location is already obvious, someone might say:

• 그 부부는 주말마다 산책해요.

Korean is very context-dependent, so full sentences like this are common for learning, but real conversation often drops parts that are already understood.