oneureun waipaiga jal dwaeseo sueop yeongsangeul bwayo.

-은/는 is the topic marker. So 오늘은 means as for today or today, ....

In this sentence, it sets the scene for what is true today. It can also carry a slight contrast, like today (unlike some other days) the Wi‑Fi is working well.

So 오늘은 is not just today as a time word; it is today as the topic of the sentence.

Here, 와이파이 is the subject of 잘 되다 (to work well / function well), so -이/가 is very natural:

• 와이파이가 잘 되다 = the Wi‑Fi works well

If you said 와이파이는, it would sound more contrastive, like:

• As for the Wi‑Fi, it works well
• maybe implying comparison with something else

Because 오늘은 is already the main topic, using 와이파이가 helps the sentence sound more natural and balanced.

잘 means well, and 돼서 comes from 되다 plus -아서/어서.

So:

• 잘 되다 = to go well / to work well / to function properly
• 잘 돼서 = because it works well or since it’s working well

In this sentence, -아서/어서 gives the reason for the second action:

• 오늘은 와이파이가 잘 돼서 수업 영상을 봐요.
• Today, because the Wi‑Fi is working well, I watch/am watching the class video.

Yes, 되다 often means to become, but it is also very commonly used to mean to work, to be possible, or to function.

With technology or connections, Korean often uses 되다 / 안 되다:

• 와이파이가 안 돼요. = The Wi‑Fi doesn’t work.
• 인터넷이 잘 돼요. = The internet works well.
• 프린터가 안 돼요. = The printer isn’t working.

So in everyday Korean, 와이파이가 잘 되다 is a very natural way to say the Wi‑Fi is functioning properly.

돼서 is the contracted form of 되어서.

The steps are:

• 되다
• 되어
• 돼
• 되어서 → 돼서

This contraction is extremely common in normal speech and writing.

So both are grammatically related, but 돼서 is the form you will hear and see much more often in everyday Korean.

수업 means class or lesson, and 영상 means video.

So 수업 영상 means:

• class video
• lesson video
• lecture video

Depending on context, it could be a recorded class, an online lesson video, or a lecture clip.

The object marker is:

• -을 after a consonant
• -를 after a vowel

영상 ends in the consonant sound ㅇ, so it takes -을:

• 영상 + 을 = 영상을

So:

• 수업 영상을 봐요 = I watch/am watching the class video

봐요 is the usual contracted form of 보아요.

From the verb 보다 (to see/watch):

• 보다
• 보아요
• 봐요

So 봐요 is just the normal polite present form used in everyday Korean.

This contraction is very common, and learners should get used to seeing 봐요 much more often than 보아요.

It can do both in different contexts, but here the most natural meaning is because/since.

So this sentence is understood as:

• Because the Wi‑Fi is working well, I’m watching the class video.

Sometimes -아서/어서 simply links actions in sequence:

• 집에 가서 쉬어요. = I go home and rest.

But in this sentence, the first clause clearly explains the reason for the second clause.

봐요 is a non-past form, so it can mean several things depending on context:

• watch
• am watching
• will watch

In this sentence, the most natural reading is something like:

• I’m watching the class video
• or I watch the class video
• possibly I’ll watch the class video, depending on situation

What it does not mean is past tense. If it were past, you would say 봤어요.

It is omitted, which is very normal in Korean.

The sentence does not explicitly say I, but from context, the person who is watching the class video is understood to be the speaker. Korean often leaves out subjects when they are obvious.

So the sentence naturally means:

• Today, because the Wi‑Fi is working well, I’m watching the class video.

Even though 저는 or 제가 is not stated, the meaning is still clear.