Kan iemand mij helpen?

Because this is a yes/no question in Dutch. In main-clause yes/no questions, the finite verb usually comes first.

• Statement: Iemand kan mij helpen. = Someone can help me.
• Question: Kan iemand mij helpen? = Can someone help me?

This verb-first pattern is very common in Dutch questions.

Kan is the present tense singular form of the verb kunnen, which means can / to be able to.

Here are some common forms:

• ik kan = I can
• jij/je kan = you can
• hij/zij/het kan = he/she/it can
• wij/we kunnen = we can
• jullie kunnen = you all can
• zij/ze kunnen = they can

In Kan iemand mij helpen?, kan agrees with iemand, which is grammatically singular.

Iemand is the normal Dutch word for someone / anybody. It does not become iemanden in standard Dutch.

So:

• iemand = someone
• niemand = no one
• iedereen = everyone

In this sentence, iemand is the subject: Can someone help me?

Because mij is the object form of the pronoun, while ik is the subject form.

• ik = I
• mij = me

So:

• Ik help iemand. = I help someone.
• Iemand helpt mij. = Someone helps me.

In Kan iemand mij helpen?, iemand is doing the action, and mij receives it.

Yes. Me is very common in everyday Dutch.

So these both work:

• Kan iemand mij helpen?
• Kan iemand me helpen?

The version with mij can sound a little more careful, clear, or slightly more formal/emphatic, while me is more common in casual speech.

Because kan is a modal verb. In Dutch, when a modal verb like kunnen is used with another verb, the second verb usually goes to the end in the infinitive form.

So:

• Ik kan helpen. = I can help.
• Kan iemand mij helpen? = Can someone help me?

This is a very important Dutch word-order pattern.

Other examples:

• Ik wil koffie drinken. = I want to drink coffee.
• Zij moet morgen werken. = She has to work tomorrow.

Because after a modal verb like kan, Dutch uses the infinitive of the main verb.

So:

• iemand helpt mij = someone helps me
• iemand kan mij helpen = someone can help me

After kan, you do not use helpt. You use helpen.

It is perfectly normal and polite in many situations, especially when asking generally if anyone can help.

It sounds like:

• Can someone help me?

If you want to sound even more polite, you could say:

• Kan iemand mij alstublieft helpen? = Can someone please help me?
• Kunt u mij helpen? = Can you help me? (formal singular/plural)
• Kun je me helpen? = Can you help me? (informal singular)

So the original sentence is fine, but adding alstublieft makes it more explicitly polite.

The difference is who you are asking.

• Kan iemand mij helpen? = Can someone help me?
  You are asking a group or asking generally if anybody is available.

• Kunt u mij helpen? = Can you help me?
  You are speaking directly to one person in a formal way, or to several people politely.

So if you are in a shop and speaking to an employee directly, Kunt u mij helpen? is often more natural. If you are calling out to a room or asking generally, Kan iemand mij helpen? fits well.

Sometimes, yes, depending on context. Dutch kunnen mainly expresses ability or possibility, but in polite requests it can overlap with English can and sometimes could.

So:

• Kan iemand mij helpen? usually means Can someone help me?
• In real use, it can also function as a request, much like English Could someone help me?

Dutch often uses the same structure where English might choose can or could depending on politeness.

Yes, it is different.

• mij is usually pronounced roughly like English my
• mei sounds more like English may

In everyday speech, many speakers reduce mij to me when it is unstressed:

• Kan iemand me helpen?

That is one reason me is so common in speech.

Often yes. In many real situations, Kan iemand mij helpen? is a natural Dutch equivalent for both:

• Can someone help me?
• Could someone help me?

If you want to sound a little softer or more polite, you can add alstublieft:

• Kan iemand mij alstublieft helpen?

Dutch does not always need a separate form matching English could.

Yes. The pattern is:

finite verb + subject + object + infinitive

So in this sentence:

• Kan = finite verb
• iemand = subject
• mij = object
• helpen = infinitive

This is a very useful model for similar Dutch questions:

• Kan hij ons bellen? = Can he call us?
• Kan zij je helpen? = Can she help you?
• Kan niemand dit doen? = Can nobody do this?

Once you recognize that pattern, many Dutch questions become much easier to understand.