Amestec ciorba înainte să o pun la microunde.

Because the verb a amesteca conjugates as:

• eu amestec
• tu amesteci
• el/ea amestecă
• noi amestecăm
• voi amestecați
• ei/ele amestecă

So amestec is simply the correct 1st person singular present form: I stir / I mix.

Romanian verbs do not always form eu with -ez. Some do, but a amesteca is not one of them.

This is about the definite article.

• ciorbă = a soup / soup
• ciorba = the soup

In Romanian, the definite article is usually attached to the end of the noun:

• băiat = boy
• băiatul = the boy

So here:

• ciorbă → ciorba

That means the sentence is talking about a specific soup, not soup in general.

Usually yes, but it has a more specific cultural meaning.

In Romanian:

• supă often means a clearer, lighter soup
• ciorbă usually means a more substantial soup, often slightly sour

In English, both are often translated simply as soup, but Romanian distinguishes them more clearly.

So a learner should know that ciorbă is not just any random soup word; it refers to a very common Romanian type of soup.

Înainte să means before followed by a verb clause.

So:

• înainte să o pun = before I put it

Romanian commonly uses înainte să + subjunctive when one action happens before another.

Another possible structure is:

• înainte de a o pune

That also means before putting it / before I put it.

Both are correct, but:

• înainte să + verb is very common in everyday speech
• înainte de a + infinitive can sound a little more formal or compact

Because after să, the verb goes into the subjunctive, and for a pune the forms are:

• să pun
• să pui
• să pună
• să punem
• să puneți
• să pună

So să o pun means that I put it / for me to put it, and in this sentence it works as before I put it.

Pune is not the right form here.
You might see pune as:

• the imperative: Pune supa pe masă! = Put the soup on the table!
• or part of other structures, but not this one

O is the direct object pronoun meaning it.

It refers back to ciorba. Since ciorba is a feminine singular noun, the pronoun is o.

So:

• ciorba = the soup
• o = it

Romanian usually places this short object pronoun before the verb:

• o pun = I put it
• o văd = I see it
• o mănânc = I eat it

English puts it after the verb, but Romanian often puts o before the verb.

Yes, absolutely.

You could say:

• Amestec ciorba înainte să pun ciorba la microunde.

But that repeats ciorba, which sounds heavier and less natural.

Using the pronoun is smoother:

• Amestec ciorba înainte să o pun la microunde.

So the sentence avoids repetition by replacing the second ciorba with o.

Yes, word-for-word it can seem strange to an English speaker, but la microunde is a very common Romanian way to mean in the microwave or into the microwave.

It is short for something like:

• în cuptorul cu microunde = in the microwave oven

In everyday Romanian, people often just say:

• la microunde

Examples:

• Încălzesc mâncarea la microunde. = I heat the food in the microwave.
• Pun laptele la microunde. = I put the milk in the microwave.

So this is something best learned as a natural expression, not translated word-for-word.

In this sentence, to stir is probably the most natural translation.

A amesteca can mean both:

• to mix
• to stir

Which one fits depends on context.

With soup, especially before heating it, English usually prefers stir:

• I stir the soup before putting it in the microwave.

So the Romanian verb is broader, but the context makes stir the best choice here.

The main clause is:

• Amestec ciorba
  I stir the soup

This follows a normal Romanian Subject-understood + Verb + Object pattern. Romanian often omits the subject pronoun because the verb ending already shows who is doing the action.

So instead of saying:

• Eu amestec ciorba

it is more natural to say:

• Amestec ciorba

Then the second part:

• înainte să o pun la microunde
  before I put it in the microwave

So the full structure is:

• [Verb + object] + [time clause]

Very natural Romanian word order.

Yes, grammatically that is correct.

But in Romanian, the subject pronoun eu is often omitted unless you want emphasis or contrast.

So:

• Amestec ciorba... = neutral, natural
• Eu amestec ciorba... = I stir the soup... maybe contrasting with someone else

For example:

• Tu încălzești pâinea, eu amestec ciorba.
  You heat the bread, I stir the soup.

So in your sentence, leaving out eu is the most natural default.