Custa-me falar em público.

Yes, custar often means to cost, but in this sentence it has another very common meaning: to be difficult, to be hard, or to take effort.

So:

• Isto custa muito. = This costs a lot.
• Custa-me falar em público. = It is hard for me to speak in public.

This second use is very common in Portuguese.

-me means to me / for me here.

In Custa-me falar em público, the idea is literally something like:

• Speaking in public is difficult to me
• more natural English: I find it hard to speak in public

In European Portuguese, object pronouns like me, te, lhe, nos are very often attached to the verb after it in affirmative main clauses. That is why you get custa-me rather than me custa.

In European Portuguese, the normal pattern in a simple affirmative sentence is enclisis, meaning the pronoun comes after the verb:

• custa-me
• diz-me
• ajuda-me

So Custa-me falar em público is the expected European Portuguese form.

In some other varieties, especially in Brazilian Portuguese, you may hear me custa, but that is not the usual standard European Portuguese pattern here.

Because in Portuguese, when an unstressed object pronoun is attached after the verb, it is normally written with a hyphen.

Examples:

• custa-me
• diz-me
• explica-me
• ajudou-me

So the hyphen is just the normal spelling rule for this kind of verb + clitic pronoun combination.

The subject is the whole infinitive phrase:

• falar em público

So the structure is basically:

• [Falar em público] custa-me.

In other words, speaking in public is the thing that is difficult for me.

That is why custa is in the 3rd person singular: the infinitive clause is treated as a single idea.

Because after custar in this structure, Portuguese uses an infinitive phrase to describe the action that is difficult.

So:

• Custa-me falar em público.
• Custa-me acordar cedo.
• Custa-nos perceber isto.

This works like English It’s hard for me to speak in public, where to speak is also an infinitive.

Yes, you can.

Both are grammatically correct:

• Custa-me falar em público.
• Falar em público custa-me.

The first one is probably the more natural everyday order in many contexts.

The second puts more focus on falar em público as the topic. It can sound slightly more marked or emphatic, but it is perfectly correct.

Em público means in public.

It is a fixed expression used for doing something where other people are present or watching.

Examples:

• falar em público = to speak in public
• chorar em público = to cry in public
• aparecer em público = to appear in public

So here, falar em público is the standard way to say to speak in public.

Yes. That is a perfectly good alternative.

Compare:

• Custa-me falar em público.
• Para mim, é difícil falar em público.

They are close in meaning, but the feeling is slightly different:

• Custa-me falar em público often suggests personal difficulty, effort, or discomfort
• É difícil para mim falar em público sounds a bit more neutral and descriptive

Another common alternative is:

• Tenho dificuldade em falar em público. = I have difficulty speaking in public.

Yes, but only when you want emphasis or contrast.

For example:

• A mim custa-me falar em público, mas ao meu irmão não.

That means something like:

• I find it hard to speak in public, but my brother doesn’t.

Without special emphasis, just Custa-me falar em público is enough.

No. In European Portuguese, negation usually pulls the pronoun before the verb.

So:

• Custa-me falar em público.
• Não me custa falar em público.

Notice the change:

• affirmative: custa-me
• negative: não me custa

This is a very important pattern in European Portuguese.

No, not in this structure.

You say:

• Custa-me falar em público.

without a before falar.

After custar with this meaning, Portuguese normally uses a direct infinitive:

• Custa-me aceitar isso.
• Custa-lhe entender a situação.
• Custa-nos esperar.

So a falar would be wrong here.

It is completely natural and common in everyday European Portuguese.

It sounds normal in speech and writing. It is neither especially formal nor especially informal.

A native speaker might also say similar things like:

• Custa-me levantar cedo.
• Custa-me dizer isto.
• Custa-me acreditar.

So this is a very useful pattern to learn.