Robo una carta ahora.

Here, robo is the first-person singular present indicative form of robar: I steal.

So:

• robar = to steal
• robo = I steal

Be careful: robo can also be a noun meaning robbery or theft, but in this sentence it is clearly the verb because it is followed by the object una carta.

Spanish often leaves out subject pronouns when they are not needed.

So instead of saying:

• Yo robo una carta ahora.

it is very common to say:

• Robo una carta ahora.

The verb form robo already tells you the subject is I, so yo is optional.
You would usually add yo only for emphasis, contrast, or clarity.

For example:

• Yo robo una carta, no tú. = I steal a letter/card, not you.

In Spanish, singular countable nouns usually need an article or another determiner.

So:

• una carta = a letter / a card

Saying just robo carta would sound incomplete or unnatural in standard Spanish.

Common options would be:

• robo una carta = I steal a letter/card
• robo la carta = I steal the letter/card
• robo esa carta = I steal that letter/card

Carta can mean different things depending on context. Common meanings include:

• letter
• card
• sometimes menu in other contexts

So without context, una carta could be:

• a letter
• a card

The meaning you choose depends on the translation or situation you were given.

Yes, ahora can move around. Spanish word order is often more flexible than English.

These are all possible:

• Robo una carta ahora.
• Ahora robo una carta.
• Robo ahora una carta. (less common, but possible in some contexts)

The version with ahora at the end is natural and straightforward. It puts the time information after the main action.

It can often be understood as either, depending on context.

In Spanish, the simple present can sometimes express what is happening right now, especially when words like ahora are included.

So:

• Robo una carta ahora can mean I steal a letter/card now
• and in many contexts it can also be understood as I am stealing a letter/card now

If you want to emphasize an action in progress more explicitly, Spanish often uses:

• Estoy robando una carta ahora. = I am stealing a letter/card now.

Still, Robo una carta ahora is grammatically correct.

Often, yes, if the speaker wants to stress that the action is happening at this very moment.

Compare:

• Robo una carta ahora. = simple present; can mean I steal / I am stealing now, depending on context
• Estoy robando una carta ahora. = present progressive; clearly I am stealing now

In everyday speech, many speakers prefer estoy + gerundio for an action currently in progress. But the simple present is still possible, especially with ahora.

The personal a is usually used before specific people or sometimes personified beings, not before ordinary inanimate objects.

So:

• Robo una carta → no a, because carta is a thing

Compare:

• Veo a María. = I see María.
• Veo una carta. = I see a letter/card.

Since una carta is not a person, there is no personal a.

Yes, and the accent mark matters a lot.

• robo = I steal
• robó = he/she/you-formal stole

The written accent in robó shows that the stress falls on the last syllable:

• RO-bo = robo
• ro-BÓ = robó

So the accent changes both pronunciation and meaning.

Yes, a little. It is grammatically fine, but it may feel unusual because people do not often say I steal a letter/card now without any context.

A native speaker would probably expect a situation such as:

• a game
• a dramatic story
• a joke
• a confession
• a card game where carta means card

So the sentence works well for grammar practice, even if it is not the most everyday sentence.

Yes. That is correct too.

• Robo una carta ahora.
• Yo robo una carta ahora.

Both are grammatical. The version without yo is more neutral and more common unless you want emphasis.

So:

• without yo = normal, everyday Spanish
• with yo = more emphasis, contrast, or clarity

The direct object is una carta.

Breakdown:

• Robo = verb
• una carta = direct object, the thing being stolen
• ahora = time expression, now

So the structure is:

[verb] + [direct object] + [time expression]

That is a very common Spanish sentence pattern.