syukudai no fairu wo appuroodositara, sensei ni renrakusimasu.

の links two nouns together. Here, 宿題のファイル means something like:

• the homework file
• the file for the homework
• the homework-related file

So 宿題 modifies ファイル. In English, we often just stack nouns, but in Japanese, の is a very common way to connect them.

を marks the direct object of the verb. The thing being uploaded is ファイル, so:

• ファイルをアップロードする = to upload the file

Even though アップロードする is partly a borrowed English word, it behaves like a normal Japanese verb phrase, so it still takes を for the object.

アップロードしたら is the -たら form of アップロードする.

Breakdown:

• アップロードする = to upload
• アップロードした = uploaded / did upload
• アップロードしたら = when/if I upload; after I upload

In this sentence, it most naturally means:

• when I’ve uploaded it
• after I upload it

So the sentence describes what the speaker will do once that action is completed.

Both can sometimes be translated as after, but they are not exactly the same.

• V-てから clearly means after doing V
• V-たら can mean when, if, or after, depending on context

In this sentence:

• アップロードしてから、先生に連絡します。 = After uploading it, I’ll contact the teacher.

• アップロードしたら、先生に連絡します。 = When/after I upload it, I’ll contact the teacher.

Here, たら sounds very natural because it presents the upload as the condition or trigger for the next action. It is a little broader and more flexible than てから.

This is a very common point of confusion.

In ～たら, the past form does not necessarily mean past time. It is just part of the grammar pattern.

So:

• アップロードしたら does not mean if I uploaded in the past
• it means if/when I upload or after I upload

Japanese often uses the plain past form inside certain grammar patterns without making the whole sentence past-tense in meaning.

に marks the target/recipient of the communication.

• 先生に連絡する = to contact the teacher
• literally, to make contact to the teacher

With 連絡する, the person you contact is usually marked with に.

Using を here would be unnatural in standard Japanese for this meaning.

連絡します means to contact, to get in touch, or to inform.

It is different from:

• 話します = speak, talk
• 言います = say

So 先生に連絡します means:

• I will contact the teacher
• I will get in touch with the teacher
• I will let the teacher know

It does not specifically say how the contact happens. It could be by message, email, app, etc.

します is the polite form of する.

• 連絡する = plain form
• 連絡します = polite form

Since this is a normal polite statement, します is used. Japanese often mixes a plain form before a grammar pattern and a polite form at the end of the sentence:

• アップロードしたら → plain form used before たら
• 連絡します → polite final verb

That combination is completely natural.

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

So this sentence does not explicitly say I, but the natural interpretation is:

• I’ll contact the teacher after I upload the homework file.

The speaker is understood to be the one uploading the file and contacting the teacher, unless context suggests otherwise.

It can, but Japanese often does not mark singular/plural or articles as clearly as English does.

So 宿題のファイル could mean:

• the homework file
• a homework file
• the file for the homework assignment

In context, people usually understand which file is meant. Japanese does not need words like a or the as often as English does.

It is a borrowed word from English, written in katakana as ファイル, but you should not assume it always matches English perfectly in every context.

Here, ファイル most naturally means a computer file. In modern Japanese, especially with アップロードする, that meaning is very clear.

So in this sentence, 宿題のファイル means the digital file containing the homework.

Yes, grammatically たら can sometimes be translated as if. But in this sentence, the most natural reading is when/after I upload the file.

Why?

Because the second action, contacting the teacher, sounds like the planned next step once the upload is done. So it feels less like a hypothetical if and more like a sequence:

1. upload the file
2. contact the teacher

So while if is possible as a grammar gloss, when/after is usually the better translation here.

Without extra context, it most naturally sounds like a specific future plan:

• Once I upload the homework file, I’ll contact the teacher.

However, Japanese present/polite non-past forms can sometimes describe repeated behavior too. If this were said in a context about a routine, it could mean something like:

• Whenever I upload the homework file, I contact the teacher.

Still, the default reading here is a one-time future action.

The comma helps separate the conditional clause from the main clause:

• アップロードしたら、 = when/after I upload it,
• 先生に連絡します。 = I’ll contact the teacher.

Japanese punctuation is somewhat flexible, but this comma makes the sentence easier to read and reflects a pause. It is very common after a clause like ～たら.