Cuanto más larga es la pendiente, más despacio pedaleamos.

It’s a very common Spanish pattern meaning the more..., the more... or the more..., the less..., depending on the second part.

So here:

• Cuanto más larga es la pendiente, más despacio pedaleamos.

literally works like:

• The longer the slope is, the more slowly we pedal.

This structure is called a correlative comparative. A few similar examples:

• Cuanto más estudias, más aprendes. = The more you study, the more you learn.
• Cuanto más tarde salimos, más tráfico hay. = The later we leave, the more traffic there is.

In everyday Spanish, you will also often see mientras más... in much of Latin America:

• Mientras más larga es la pendiente, más despacio pedaleamos.

That version is common in speech, but cuanto más is widely understood and very standard.

Because cuanto here is not a question word and has nothing to do with when.

Compare:

• cuándo = when
  
  • ¿Cuándo llegas? = When are you arriving?
• cuanto = part of a comparison pattern like the more...
  
  • Cuanto más comes, más engordas. = The more you eat, the more you gain weight.

So:

• cuándo has an accent and asks about time.
• cuanto here has no accent because it is being used as part of a grammatical comparison structure, not as an interrogative word.

Because larga agrees with la pendiente, which is a feminine singular noun.

• la pendiente = the slope / incline
• so the adjective must match:
  • larga = feminine singular

Agreement in Spanish works like this:

• el camino largo = the long path
• la pendiente larga = the long slope
• los caminos largos = the long paths
• las pendientes largas = the long slopes

So in the sentence, más larga means longer, and it matches la pendiente.

Because the sentence is describing an inherent characteristic of the slope, not a temporary condition.

In Spanish:

• ser is usually used for identity, description, and essential characteristics
• estar is usually used for states, conditions, or location

Here, larga describes what the slope is like:

• la pendiente es larga = the slope is long

That’s why es is natural.

If you used está larga, it would sound unusual in this context because length is not normally treated as a temporary state.

Because despacio is functioning as an adverb, and it modifies the verb pedaleamos.

• pedaleamos = we pedal
• despacio = slowly

So:

• más despacio pedaleamos = we pedal more slowly

Compare adjective vs. adverb:

• lento / lenta = slow, as an adjective
  
  • una bicicleta lenta = a slow bicycle
• despacio = slowly, as an adverb
  
  • pedaleamos despacio = we pedal slowly

You could also say:

• pedaleamos más lentamente

But más despacio is usually more common and natural in everyday speech.

Here pendiente means slope, incline, or hill grade.

Depending on context, pendiente can mean different things in Spanish, for example:

• slope / incline
• earring (especially in Spain)
• pending / unfinished in expressions like tengo algo pendiente

But in this sentence, because of pedaleamos, it clearly means a road or path with an incline:

• la pendiente = the slope / incline

So the sentence is talking about cycling uphill or on a longer incline.

Because Spanish often uses the present tense to express general truths, habits, or things that typically happen.

Here the meaning is not about one single moment only. It expresses a general pattern:

• when the slope is longer, we pedal more slowly

So pedaleamos means:

• we pedal
• or in context, we tend to pedal

This is very normal in Spanish. Compare:

• Cuando hace frío, usamos abrigo. = When it’s cold, we wear a coat.
• Cuanto más practicamos, mejor hablamos. = The more we practice, the better we speak.

Usually, in normal modern Spanish, it is more natural to keep the verb:

• Cuanto más larga es la pendiente, más despacio pedaleamos.

A version without es may appear in more compressed, literary, or headline-like styles, but it is not the most straightforward form for learners.

So as a learner, it’s best to use the full structure with the verb:

• Cuanto más + adjective + ser, más...

For example:

• Cuanto más difícil es el examen, más nerviosos estamos.

Yes, a little.

The most neutral version is:

• Cuanto más larga es la pendiente, más despacio pedaleamos.

But Spanish allows some flexibility, especially in the second part:

• Cuanto más larga es la pendiente, pedaleamos más despacio.

This version is also very natural.

Both mean the same thing. The difference is mostly rhythm and emphasis.

For learners, the safest pattern is:

• Cuanto más..., más...
• or
• Cuanto más..., subject + verb + más...

No. In much of Latin America, many speakers also use mientras más or entre más.

So you may hear:

• Mientras más larga es la pendiente, más despacio pedaleamos.
• Entre más larga es la pendiente, más despacio pedaleamos.

These are common in different regions of Latin America.

Still, cuanto más is a very solid option because it is standard and widely understood everywhere.

It means longer.

Spanish usually forms comparatives with:

• más + adjective

So:

• más largo / más larga = longer
• más alto / más alta = taller
• más difícil = more difficult

That is why:

• más larga = longer

Even though the literal pieces are more long, the real English translation is simply longer.

Because this is a comparison, not a superlative.

Here, más despacio means more slowly in relation to something else:

• the longer the slope, the more slowly we pedal

If you said lo más despacio, that would suggest as slowly as possible or the most slowly, which is a different idea.

Compare:

• Pedaleamos más despacio. = We pedal more slowly.
• Pedaleamos lo más despacio posible. = We pedal as slowly as possible.

So in your sentence, plain más despacio is exactly what you want.