wakaranaikoto ga attara, kigaru ni kiite kudasai.

Yes. 分からない and わからない both mean don’t understand / don’t know in this kind of sentence.

A few notes:

• 分かる is very often written in kana as わかる, especially in everyday writing.
• Writing it as 分かる / 分からない is also common and perfectly correct.
• The meaning does not change here.

So 分からないことがあったら and わからないことがあったら are basically the same.

Literally, it means a thing that is not understood or something you don’t understand.

Breakdown:

• 分からない = not understood / don’t understand
• こと = thing, matter, fact

So:

• 分からないこと = something you don’t understand
• In natural English: if there’s anything you don’t understand...

Here, こと turns the idea not understanding into a noun-like expression: things you don’t understand.

The が marks 分からないこと as the thing that exists / happens with ある.

Structure:

• 分からないこと = something you don’t understand
• がある = there is / there exists

So:

• 分からないことがある = there is something you don’t understand

Then:

• 分からないことがあったら = if there is something you don’t understand

Why not を? Because ある usually takes が, not を, for the thing that exists.

あったら is the たら-form of ある.

• ある = to exist, to have
• あった = existed / was
• あったら = if there is / if there happens to be

In this sentence, ～たら makes a condition:

• 分からないことがあったら = if there is anything you don’t understand

This kind of if is very common in Japanese.

Because the meaning is slightly different.

• 分からなかったら = if you don’t understand
• 分からないことがあったら = if there is something you don’t understand

Both are natural, but the version in your sentence sounds a little softer and more general. It refers to any questions or unclear points rather than directly saying if you don’t understand.

So this sentence feels polite and helpful, like:

• If anything is unclear, please ask freely.

気軽に means something like:

• without hesitation
• freely
• feel free to
• casually / comfortably

It comes from 気軽(な), which means easygoing, casual, or without feeling burdened.

In this sentence, it tells the listener not to worry about asking. So 気軽に聞いてください means:

• Please feel free to ask.

It does not mean careless or rude. It means the speaker wants the listener to ask comfortably.

Because 気軽 is a na-adjective / adjectival noun, and here it is being used adverbially to modify 聞いてください.

Compare:

• 気軽な人 = an easygoing person
• 気軽に聞く = ask casually / feel free to ask

So に is what lets 気軽 describe the verb 聞く.

Good question. 聞く can mean both to ask and to hear/listen, depending on context.

Here it clearly means ask, because of the earlier part:

• 分からないことがあったら = if there’s something you don’t understand

So 聞いてください here means:

• please ask

If the context were about audio or music, 聞く could mean listen instead.

It is the て-form of 聞く plus ください.

Breakdown:

• 聞く = ask / listen
• 聞いて = te-form
• ください = please do...

So:

• 聞いてください = please ask

This is a standard polite request pattern:

• Vてください = please do V

Examples:

• 見てください = please look
• 待ってください = please wait
• 教えてください = please tell me / please teach me

The subject is omitted, which is very normal in Japanese.

The sentence is understood as addressing you, even though you is not stated:

• 分からないことがあったら、気軽に聞いてください。
• If there’s anything you don’t understand, please feel free to ask.

Japanese often leaves out subjects and objects when they are obvious from context.

So even without あなた, the listener understands that:

• you are the one who may not understand something
• you are the one being told to ask

The comma separates the condition from the main request.

• 分からないことがあったら、 = if there’s anything you don’t understand,
• 気軽に聞いてください。 = please feel free to ask.

Japanese commas are often used to make the sentence easier to read, especially when the first part sets up a condition, topic, or time expression.

The comma is helpful, but punctuation in Japanese is sometimes more flexible than in English.

Yes. A very natural English translation would be:

• If you have any questions, feel free to ask.
• If there’s anything you don’t understand, please feel free to ask.
• If anything is unclear, don’t hesitate to ask.

Even though 分からないこと literally means things you don’t understand, in natural English it often becomes questions or anything unclear.

Yes, it is polite and friendly.

Why:

• ください makes it a polite request
• 気軽に makes it sound warm and approachable
• The overall tone is common in teaching, customer service, work, and everyday helpful situations

It is not extremely formal, but it is very natural and appropriate in polite conversation.

A rough tone scale:

• 聞いて。 = ask me (casual)
• 聞いてください。 = please ask (polite)
• お気軽にお聞きください。 = please feel free to ask (more formal/polite)

So your sentence is polite, standard, and welcoming.