asita ha siken ga arimasu. dakara, konya ha hayaku nemasu.

It is read:

あした は しけん が あります。だから、こんや は はやく ねます。

In normal Japanese writing, it would usually appear without spaces:

明日は試験があります。だから、今夜は早く寝ます。

A few useful readings here are:

• 明日 → あした
• 試験 → しけん
• 今夜 → こんや
• 早く → はやく
• 寝ます → ねます

The spaces are just for learners. Standard Japanese normally does not use spaces between words.

So a natural written version is:

明日は試験があります。だから、今夜は早く寝ます。

Textbooks often add spaces to make the grammar easier to see.

Here, は marks the topic.

• 明日は = as for tomorrow
• 今夜は = as for tonight

It sets the time frame for each sentence.

This is very common in Japanese. Instead of always saying a subject like I, Japanese often introduces a time or situation as the topic.

Also, with time words, は can add a slight feeling of contrast or emphasis:

• 今夜は早く寝ます = As for tonight, I’ll go to bed early

That can sound a little like at least tonight or tonight in particular.

Yes, often you can.

For example:

• 明日、試験があります。
• 今夜、早く寝ます。

These are also natural.

The version with は sounds a bit more like the speaker is setting up each time expression as a topic:

• Tomorrow, there is an exam.
• So, tonight, I’m going to bed early.

So は is not required in every case, but it gives structure and emphasis.

Because words like 今日, 明日, and 昨日 usually do not take に.

So you normally say:

• 明日試験があります
• not 明日に試験があります

Japanese often uses に with specific times such as:

• 3時に
• 月曜日に
• 7月1日に

But relative day words like today, tomorrow, and yesterday usually appear without に.

Because が marks the thing that exists or occurs with あります.

In this sentence:

• 試験があります = there is an exam / an exam will take place

So 試験 is the thing being identified as existing or happening, and が marks that.

Why not を?
Because 試験 is not a direct object here. The verb is not taking an exam; it is there is an exam.

Why not は?
You can say 試験はあります, but that changes the nuance. It sounds more contrastive, like:

• As for the exam, there is one
• or There is an exam, at least

In this sentence, が is the most straightforward choice.

Yes, ある / あります is used for non-living things, but in Japanese it is also very commonly used for events and scheduled occurrences.

So these are all natural:

• 会議があります = There is a meeting
• 授業があります = There is class
• 試験があります = There is an exam

So 試験があります means the exam exists on the schedule, or the exam will take place.

Also, because 試験 is not a living thing, Japanese uses あります, not います.

Yes, it could.

• 明日は試験があります = There is an exam tomorrow
• 明日は試験です = Tomorrow is the exam or I have an exam tomorrow

Both are natural, but the nuance is a little different.

試験があります focuses on the existence or occurrence of the exam.
試験です is more like identifying what tomorrow is in relation to the speaker.

In beginner Japanese, both patterns are useful.

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

In English, you usually need to say I:

• I will go to bed early

In Japanese, if it is obvious that the speaker is talking about themself, 私は is often omitted.

So:

• 今夜は早く寝ます

naturally means:

• I’ll go to bed early tonight

without needing to say 私は.

Japanese -ます forms are usually called non-past. That means they can refer to:

• present
• habitual action
• future

The time word tells you which meaning is intended.

Here, because the sentence says 今夜, 寝ます clearly means the future:

• Tonight, I will go to bed early

Japanese does not have a separate future tense in the same way English does.

Because 早い is an i-adjective, and when an i-adjective modifies a verb, it changes to -く form.

So:

• 早い = early
• 早く = early / quickly, used adverbially

Here it modifies 寝ます, so:

• 早く寝ます = go to bed early

This is the same pattern you see in other adjectives:

• 速い → 速く
• 遅い → 遅く
• 高い → 高く

だから means so, therefore, or that’s why.

It connects the first sentence to the second:

• Tomorrow there is an exam. Therefore, tonight I’ll go to bed early.

It is a very common way to show cause and result.

It is natural in conversation and ordinary writing. Depending on style, you may also see:

• ですから = more formal
• なので = softer / often very common in speech
• そのため = more formal written style

Yes. That is very common.

Japanese often uses connectors like だから at the beginning of a new sentence, just like English uses So or Therefore.

So this structure is completely natural:

• 明日は試験があります。だから、今夜は早く寝ます。

You could also combine the idea into one sentence, for example:

• 明日は試験がありますから、今夜は早く寝ます。

That means roughly:

• Because there is an exam tomorrow, I’m going to bed early tonight.

Not completely, but the verb usually comes at the end.

This sentence follows a very common pattern:

• time/topic
• subject or main item
• adverb
• verb

So:

• 明日は / 試験が / あります
• 今夜は / 早く / 寝ます

Japanese word order is more flexible than English, but not random. The particles help show each word’s role.

For a beginner, this sentence is a very good model of normal word order.