Learn Hardcore Portuguese (Portugal): Muita gente acha que o exame é difícil. - Many people think that the exam is difficult.

In Portuguese, gente is grammatically singular, even though it refers to a group of people.
Because of that, the verb agrees with gente in the singular: muita gente acha.

If you actually make the subject grammatically plural, the verb changes too:

Muitas pessoas acham que o exame é difícil.

What is the difference between muita gente and muitas pessoas?

Both mean many people / a lot of people, and in most contexts you can use either.

Nuance:

muita gente is very common in everyday speech and sounds a bit more informal/natural in conversation.
muitas pessoas is neutral and can be slightly more “literal” or a bit more formal.

In this sentence, muita gente acha que… is exactly how a European Portuguese speaker would naturally say it.

Why do we say muita gente and not muito gente?

Muito / muita / muitos / muitas must agree in gender and number with the noun it modifies.
Gente is grammatically feminine and singular in Portuguese, so you need the feminine singular form muita:

muita gente (a lot of people)
muitos alunos (many students – masculine plural)
muitas pessoas (many people – feminine plural)

So muito gente would be ungrammatical.

Is gente always singular? Is there a plural like gentes?

In this sense (people, folks), gente is treated as a singular collective noun, and that is by far the most common use.
So you say:

Esta gente é estranha. (verb in the singular)
Muita gente acha que…

There is a literary or special-use plural gentes (e.g. as gentes do sul), but it’s uncommon in everyday speech and you don’t use it in this kind of sentence.

What exactly does achar mean here? How is it different from pensar or acreditar?

Here achar means to think / to be of the opinion that. In European Portuguese, achar que… is the most common everyday way to express a personal opinion:

Eu acho que é difícil. = I think it’s difficult.

Roughly:

achar que = think (opinion, often a bit subjective or tentative)
pensar que = think (more neutral or logical, but still often interchangeable with achar que)
acreditar que = believe (has more of a sense of belief/conviction, not just an opinion)

In this sentence, Muita gente acha que o exame é difícil sounds more natural than Muita gente pensa que… in everyday speech.

Why is there a que after acha? Can it be left out?

Here que is a conjunction introducing a subordinate clause:

acha que o exame é difícil = thinks that the exam is difficult.

In this structure (achar que + sentence), que is normally required; you cannot just say *Muita gente acha o exame é difícil – that is incorrect.
You can omit que only in a different pattern, where achar takes a direct object and an adjective: achar o exame difícil (see next question).

Can I say Muita gente acha o exame difícil instead of acha que o exame é difícil?

Yes. Both are correct, but the structure changes slightly:

Muita gente acha que o exame é difícil.
- Pattern: achar que + full clause
- Literally: “thinks that the exam is difficult.”
Muita gente acha o exame difícil.
- Pattern: achar + object + adjective
- Literally: “finds the exam difficult / considers the exam difficult.”

In everyday speech, achar que o exame é difícil is more common and feels more neutral.
Achar o exame difícil is also natural, maybe a bit more compact or slightly more formal.

Why is it o exame and not just exame without the article?

European Portuguese uses definite articles much more than English.

O exame suggests:

a specific exam that speaker and listener can identify (for example, this year’s national exam, or the test in a particular subject).

Saying just exame é difícil would be ungrammatical here.
Without context you might say fazer exames é difícil (no article because it’s plural and generic), but with a singular concrete noun like this, you normally need o exame.

Why is it é difícil and not está difícil? What’s the difference?

Ser (é) expresses a more permanent, inherent, or characteristic quality; estar (está) expresses a temporary or changing state.

O exame é difícil.
→ The exam (as designed, in general) is difficult; that’s its nature or usual reputation.
O exame está difícil este ano.
→ This year, it’s difficult (perhaps more than usual); it implies a temporary situation or comparison with other times.

In the original sentence, speakers are giving a general opinion about how the exam is, so é difícil is the natural choice.

Is difícil masculine, feminine, or does it change?

Difícil is invariable in gender: it has the same form for masculine and feminine:

o exame é difícil (masculine singular)
a prova é difícil (feminine singular)
os exames são difíceis (masculine plural)
as provas são difíceis (feminine plural)

Only the plural changes: difícil → difíceis.

Is gente more informal than pessoas in European Portuguese?

A little, but not dramatically.

gente is very common and natural in speech: muita gente, esta gente, a nossa gente.
pessoas is neutral and can sound a bit more “textbook” or a bit more formal in some contexts.

In this exact sentence, Muita gente acha que o exame é difícil is what you’d most naturally hear in Portugal. Muitas pessoas acham… is also correct, just slightly more neutral/formal in tone.

The sentence is in the present: acha. Could this also refer to a future exam?

Yes. In Portuguese, the present tense is often used for general opinions or for things that are about to happen or happen regularly.

So Muita gente acha que o exame é difícil can mean:

people generally think this exam (whenever it happens) is difficult,
or
people already think that the upcoming exam (e.g. next week) is difficult, based on what they know.

If you want to be explicit about the future event, you could say Muita gente acha que o exame vai ser difícil, but it’s not necessary; the original is perfectly natural.