निमंत्रण भेजो, फिर जन्मदिन मनाओ।

Because they are imperative forms used with तुम.

In Hindi, if you are telling someone you (tum) to do something, the verb often ends in -ओ:

• भेजना → भेजो = send
• मनाना → मनाओ = celebrate

So this sentence is giving two commands to the listener:

• निमंत्रण भेजो = send the invitation(s)
• फिर जन्मदिन मनाओ = then celebrate the birthday

This is less formal than आप speech, but more neutral/common than the very intimate तू form.

It can be either, depending on context.

The तुम form in Hindi can be used for:

• one person you know fairly well
• more than one person

So भेजो and मनाओ could mean:

• you (singular) send... celebrate...
• you all send... celebrate...

Hindi often leaves that to context.

निमंत्रण means invitation.

In this sentence, it is the thing being sent:

• निमंत्रण भेजो = send the invitation / send invitations

Depending on context, it could refer to:

• a formal invitation
• an invite in general
• invitation cards/messages

In everyday speech, people may also use words like इनविटेशन or more specific phrases such as निमंत्रण-पत्र for invitation card/letter.

Because निमंत्रण is being used as a direct object, and Hindi does not always mark direct objects with को.

Compare:

• निमंत्रण भेजो = send the invitation / invitations
• राम को बुलाओ = call/invite Ram

को is more likely with:

• people
• specific/definite objects
• objects needing emphasis or clarification

With a general thing like निमंत्रण, leaving out को is completely normal.

Here फिर means then or after that.

So the sentence gives a sequence:

1. निमंत्रण भेजो
2. फिर जन्मदिन मनाओ

In other words: first do one action, then the next.

Be careful: फिर can also mean again in other contexts.
For example:

• फिर बोलो = say it again
• काम करो, फिर घर जाओ = do the work, then go home

So its exact meaning depends on context.

Yes, pretty much.

• जन्मदिन = birthday
• मनाओ = celebrate

So जन्मदिन मनाओ literally means celebrate the birthday.

Hindi often does not use articles like a or the, so English may need to add them when translating.

Also, मनाना is the common verb for celebrating occasions:

• जन्मदिन मनाना = celebrate a birthday
• त्योहार मनाना = celebrate a festival
• शादी की सालगिरह मनाना = celebrate a wedding anniversary

Because मनाना is the standard verb meaning to celebrate in this kind of context.

It is used with festivals, holidays, birthdays, and similar events:

• दिवाली मनाना
• होली मनाना
• जन्मदिन मनाना

So मनाओ is simply the tum-imperative form of मनाना.

Do not confuse this with unrelated verbs that may look similar.

The word order is natural and clear, but Hindi word order is somewhat flexible.

The basic pattern here is:

• object + verb
• then
• object + verb

So:

• निमंत्रण भेजो
• फिर जन्मदिन मनाओ

This is very natural in Hindi. You could sometimes rearrange parts for emphasis, but the given order is straightforward and idiomatic.

Also, the comma helps show that these are two linked commands.

You would usually switch from the तुम imperative to an आप form.

For example:

• निमंत्रण भेजिए, फिर जन्मदिन मनाइए।

or

• निमंत्रण भेजें, फिर जन्मदिन मनाएँ।

These are more polite and suitable for formal situations or respectful speech.

So the levels are roughly:

• भेज / मना = very intimate / very casual (तू)
• भेजो / मनाओ = familiar (तुम)
• भेजिए / मनाइए or भेजें / मनाएँ = polite (आप)

Yes. In a sentence like this, it can be understood either way from context.

Hindi often does not force you to mark singular vs. plural as clearly as English does in every sentence. So:

• निमंत्रण भेजो can mean send the invitation
• or send invitations

If the speaker wants to make plurality clearer, they might use context or another expression, such as:

• सभी को निमंत्रण भेजो = send invitations to everyone

A rough pronunciation guide:

• निमंत्रण ≈ ni-man-traṇ
• जन्मदिन ≈ janm-din

A few notes:

• In निमंत्रण, the त्र cluster is pronounced together.
• The final ण is a retroflex n sound.
• In जन्मदिन, the middle consonant cluster can feel compact: janm-din, not a fully separated ja-nam-di-n.

If you are a beginner, saying them a bit more clearly and slowly is fine. Clear pronunciation matters more than perfect speed.

Yes, it is understandable and natural enough, especially as a simple instruction.

It sounds like a sequence of commands:

• Send the invitations, then celebrate the birthday.

In everyday speech, a speaker might also say slightly expanded versions depending on context, such as:

• पहले निमंत्रण भेजो, फिर जन्मदिन मनाओ।
  = First send the invitations, then celebrate the birthday.

• सबको निमंत्रण भेजो, फिर जन्मदिन मनाओ।
  = Send invitations to everyone, then celebrate the birthday.

But the original sentence is perfectly fine as a simple learner example.