ima ha zyugyoutyuu desu kara, ato de renrakusimasu.

は marks 今 as the topic: as for now / right now.

So 今は does not just mean now in a neutral dictionary sense. It has a slight contrastive feel, like:

• As for now, ...
• Right now, ...

In this sentence, 今は授業中です means something like I’m in class right now or Right now, I’m in the middle of class.

Without は, 今 could still appear in other sentences, but 今は is very natural when setting up the current situation before explaining what will happen later.

授業中 means in class or more literally in the middle of a lesson/class.

It is made from:

• 授業 = class, lesson
• 中 = middle, during

So 授業中 literally means during class.

You will see 〜中 attached to many nouns to mean in the middle of ... or during ..., for example:

• 仕事中 = at work / in the middle of কাজ? no, must remain English -> at work / in the middle of working
• 会議中 = in a meeting
• 食事中 = eating / during a meal

In this sentence, 授業中です means (I am) in class.

Japanese often leaves out the subject when it is obvious from context.

In English, you usually need to say:

• I’m in class right now, so I’ll contact you later.

In Japanese, both I subjects are omitted because they are understood from the situation. The sentence naturally implies:

• I’m in class right now, so I’ll contact you later.

This is extremely common in Japanese. Learners often expect every sentence to have an explicit subject, but Japanese does not work that way.

授業中 is functioning like a noun-type predicate here, so です is used to make the sentence polite.

• 授業中です = (I am) in class

This is similar to:

• 学生です = I am a student
• 会議中です = I’m in a meeting

In casual speech, someone might say:

• 今、授業中だから、あとで連絡する。

But in polite speech, です and します are appropriate.

Here から means because / since.

So:

• 今は授業中ですから = because I’m in class right now
• あとで連絡します = I’ll contact you later

Put together, the sentence means:

• Because I’m in class right now, I’ll contact you later.

A useful thing to know is that から connects a reason to a result. The structure is:

• reason + から, result

For example:

• 忙しいですから、行けません。
  • Because I’m busy, I can’t go.

Yes. They are the same sound, but different uses.

In Japanese, から can mean:

• from
  • 日本から来ました。 = I came from Japan.
• because / since
  • 忙しいから行けない。 = I can’t go because I’m busy.

In your sentence, から clearly means because, since it follows a full clause:

• 今は授業中です
  • から

So it is not the from meaning here.

あとで means later or afterwards.

It comes from:

• あと = after, later
• で = a particle

As a set phrase, あとで means later in the sense of I’ll do it afterward / at a later time.

Examples:

• あとで行きます。 = I’ll go later.
• あとで電話します。 = I’ll call later.

It is often written in hiragana as あとで, though 後で is also possible.

Both are possible, but 連絡します is very common and natural.

連絡 is a noun meaning contact / communication, and with する it becomes a verb:

• 連絡する = to contact / to get in touch

Many noun + する verbs can appear with or without を, especially in everyday usage:

• 連絡します
• 連絡をします

Both can mean the same thing, but 連絡します is usually smoother and more common.

Yes. Japanese does not have a separate future tense like English will.

します is a non-past form, and depending on context it can mean:

• present habitual
• future

Here, because of あとで (later), it clearly refers to the future:

• あとで連絡します = I’ll contact you later

So the time word tells you how to interpret the verb.

Yes, it is polite.

The main clues are:

• です
• します

These are polite forms, so the whole sentence is suitable for speaking to someone politely, such as:

• a classmate you are not very close to
• a coworker
• a customer
• someone older or higher-status, depending on context

A more casual version would be:

• 今、授業中だから、あとで連絡する。

Yes, that is a very natural translation.

Even though the meaning has already been given, this is a useful nuance point:

• 授業中 is not just at school
• it specifically means during class / in the middle of class

So I’m in class right now and I’m in the middle of class right now are both good, depending on how literal you want to be.

The comma helps separate the reason part from the main action part.

• 今は授業中ですから、 = because I’m in class right now,
• あとで連絡します。 = I’ll contact you later.

Japanese punctuation is somewhat flexible, and you may also see similar sentences with no comma at all. The comma here simply makes the sentence easier to read.

Yes. You could say:

• 今は授業中ですので、あとで連絡します。

This is also natural and is often a bit softer or more formal than から.

Very roughly:

• から = because / since
• ので = because / so, with a slightly gentler tone

Both work, but ですから is straightforward and common in polite speech.

Yes, は can add a slight contrastive nuance.

今は can suggest something like:

• Right now, I’m in class
  (so not available now, but maybe available later)

That fits the second half perfectly:

• あとで連絡します = I’ll contact you later

So the sentence naturally contrasts now and later:

• Now: I’m in class
• Later: I’ll contact you

This is one reason 今は works especially well here.