En la autopista no me gusta acelerar; prefiero ir despacio y no adelantar a nadie.

Spanish often uses en where English uses on for roads and locations.

So en la autopista is the normal Spanish way to say on the motorway/highway.

Using sobre la autopista would usually suggest something physically above the motorway, not simply travelling on it.

In Spain, autopista means a major high-speed road, similar to motorway or highway.

It is close to autovía, but they are not always identical:

• autopista: often a more controlled-access road, sometimes with tolls
• autovía: also a major dual-carriageway road, often toll-free

For a learner, translating autopista as motorway/highway is perfectly fine in most situations.

Because gustar works differently from English to like.

In Spanish, gustar literally works more like to be pleasing to. So:

• me = to me
• gusta = is pleasing

So no me gusta acelerar is structurally closer to accelerating is not pleasing to me than to I do not like accelerating.

If you said yo no gusto, it would mean something like I am not pleasing or people don’t like me, which is a different idea.

Because the thing that is pleasing is acelerar, and an infinitive counts as a singular idea.

So:

• Me gusta acelerar
• Me gusta correr
• Me gusta leer

All of these use gusta because the whole action is treated as one singular thing.

You use gustan when what follows is plural:

• Me gustan los coches
• Me gustan las carreteras tranquilas

Because Spanish often uses the infinitive to talk about actions in a general way.

Here:

• acelerar = accelerating / to accelerate
• ir despacio = going slowly / to go slowly
• adelantar = overtaking / to overtake

After verbs like gustar and preferir, this is very common:

• Me gusta conducir
• Prefiero caminar
• No quiero correr

English sometimes uses -ing and sometimes to + verb, but Spanish often just uses the infinitive.

Because preferir is a stem-changing verb.

In many present-tense forms, the e in the stem changes to ie:

• prefiero
• prefieres
• prefiere
• preferimos
• preferís
• prefieren

So prefiero is the correct I prefer form.

Yes, conducir despacio would also be possible, but ir despacio is very natural and common.

In driving contexts, ir can mean something like:

• to go
• to be going
• to drive along

So prefiero ir despacio sounds very idiomatic, especially when the context already makes it clear that we are talking about driving.

Despacio is an adverb, meaning slowly.

That is why it works with the verb ir:

• ir despacio = to go slowly

Lento is an adjective, meaning slow, so it normally describes a noun:

• un coche lento
• un conductor lento

You may hear ir lento in some contexts, but for learners, ir despacio is the safest and most standard choice here.

You could also say lentamente, but despacio is more everyday and natural in speech.

Here adelantar means to overtake or to pass another vehicle on the road.

This is a very common driving meaning in Spain:

• adelantar a un coche
• adelantar a un camión

In other contexts, adelantar can mean other things, such as:

• to move something forward
• to bring something forward
• to make progress
• to move a date earlier

But in this sentence, it clearly refers to road traffic.

Because Spanish uses the personal a before a direct object that refers to a person.

Since nadie means no one / nobody and refers to people, you need a:

• No vi a nadie
• No conozco a nadie
• No quiero adelantar a nadie

This a does not mean to here. It is just the normal marker used before human direct objects.

Yes, it is a double negative, and that is normal in Spanish.

When a negative word like nadie, nunca, or nada comes after the verb, Spanish normally also keeps no before the verb:

• No veo a nadie
• No digo nada
• No voy nunca

So no adelantar a nadie is completely correct.

If the negative word comes before the verb, then no is usually not used:

• Nadie vino
• Nada importa

Literally, nadie means no one / nobody.

But after a negative verb, natural English often translates it as anyone:

• No veo a nadie = I don’t see anyone
• No conozco a nadie = I don’t know anyone

So in this sentence, although nadie literally means nobody, the most natural English meaning is often anyone.

Yes, that is correct.

Both are natural, but the structure is slightly different:

• Prefiero ir despacio y no adelantar a nadie
  This gives two preferred actions together: to go slowly and not overtake anyone.

• Prefiero no adelantar a nadie
  This focuses more directly on the second idea only: not overtaking anyone.

So the original sentence sounds nicely balanced because prefiero applies to both infinitive phrases:

• ir despacio
• no adelantar a nadie