Se prendo il tram, arrivo in città presto.

Because this sentence expresses a real or likely condition: if the speaker takes the tram, the result is arriving in the city early. In Italian, for real conditions, se is normally followed by the indicative, not the conditional.

So Se prendo il tram, arrivo in città presto is natural.

If the sentence were hypothetical or unlikely, Italian would usually switch to the imperfect subjunctive + conditional, for example: Se prendessi il tram, arriverei in città presto
= If I took the tram, I would arrive in the city early.

Italian often uses the present tense for:

• general truths / habitual situations
• near-future situations, especially when the context makes the timing clear

So this sentence can sound like:

• Whenever I take the tram, I get into the city early or
• If I take the tram, I’ll get into the city early

English often prefers will in the second part, but Italian very often keeps the present.

Yes. That is also correct.

The version with arriverò makes the future result more explicit:

• Se prendo il tram, arriverò in città presto = If I take the tram, I will arrive in the city early.

The original sentence with arrivo is still completely natural and often sounds more direct or conversational.

Because Italian usually drops subject pronouns when the verb ending already shows who the subject is.

• prendo already means I take
• arrivo already means I arrive

So io is not necessary unless you want emphasis or contrast:

• Io prendo il tram, non l’autobus
  = I take the tram, not the bus.

In Italian, direct objects are often used with an article where English might not use one.

Prendere il tram is the normal way to say to take the tram.

Here il can mean:

• the specific tram / tram line in context
• or more generally the tram as a means of transport

So even though English sometimes says just take tram in certain contexts, Italian normally needs il here.

Because in città is the normal Italian expression for in town / into the city.

• arrivare in città = to arrive in the city / get into town

Alla città is not natural here. It would sound like to the city in a very literal, unusual way.

Italian uses certain destination expressions idiomatically, and in città is the standard one.

Because in città is a fixed, common expression used in a general sense.

It is similar to expressions like:

• in casa
• a scuola
• in ufficio

When the idea is general rather than referring to a specific city as a named place, Italian often omits the article.

If you were talking about a specific city in a different structure, you might use an article or a name:

• arrivo a Roma
• sono nella città vecchia

But here in città simply means into town / in the city in a general way.

Presto is an adverb meaning early or soon, depending on context.

In this sentence, it most naturally means early:

• arrivo in città presto = I arrive in the city early

It tells us when the speaker arrives.

Yes, Italian word order is fairly flexible.

You could say:

• arrivo in città presto
• arrivo presto in città

Both are grammatical. The difference is mainly one of rhythm or emphasis.

The original version sounds very natural and neutral. Putting presto earlier can put slightly more focus on the time.

It is common and helpful, but in a short sentence like this, it is not absolutely required in every context.

The comma separates:

• the if-clause: Se prendo il tram
• the main clause: arrivo in città presto

So the comma makes the structure clearer and is a good choice in writing.

Yes. Prendere is a regular -ere verb in the present tense.

Its first-person singular form is:

• io prendo = I take

So:

• se prendo = if I take

The same happens with arrivare:

• io arrivo = I arrive

The first sentence is about a real or possible situation:

• Se prendo il tram, arrivo in città presto
• If I take the tram, I arrive / I’ll arrive in the city early

The second is about a hypothetical or less real situation:

• Se prendessi il tram, arriverei in città presto
• If I took the tram, I would arrive in the city early

So the difference is:

• present indicative = real, likely, practical
• imperfect subjunctive + conditional = hypothetical, imagined, less direct