Quando estou desmotivado, ponho música calma nos fones e começo devagar.

In Portuguese, subject pronouns (like eu, tu, ele) are often omitted because the verb ending already shows who the subject is.

• Estou can only mean I am in the present tense, so eu is not needed.
• Quando estou desmotivado is completely natural and very common.
• Quando eu estou desmotivado is also grammatically correct, but the eu adds a bit of emphasis, like “When I am demotivated (as opposed to others)”.

So both are correct; the version without eu is just more neutral and typical in everyday speech.

Portuguese distinguishes between:

• ser = to be (permanent/defining characteristics)
• estar = to be (temporary states, moods, locations)

Being demotivated is seen as a temporary state, not an essential permanent quality of a person. So:

• Estou desmotivado = “I’m feeling demotivated (now / in this period).”
• Sou desmotivado would sound like “I am (by nature) a demotivated person”, which is unusual and quite negative.

So estou desmotivado is the natural choice here.

Ponho is the first-person singular (eu) present tense of the verb pôr (to put).

Pôr is irregular:

• eu ponho – I put
• tu pões
• ele/ela põe
• nós pomos
• vocês / eles põem

There is no form pôo in modern standard Portuguese; ponho is the correct present form for eu.

So ponho música calma literally means “I put calm music (on)” and is understood as “I put on some calm music.”

All three are understandable, but they have slightly different feels:

• ponho música calma – very common, neutral, everyday.
• meto música calma – also common in European Portuguese, slightly more informal/colloquial; some people consider meter a bit “sloppier” in style, but it’s widely used in speech.
• coloco música calma – sounds a bit more formal or careful, and more literal “place/put”; it’s fine, but in casual speech ponho or meto are more typical.

In natural European Portuguese conversation, ponho música calma (or meto música calma) is what you’re most likely to hear.

In Portuguese, adjectives usually go after the noun:

• música calma = calm music
• dia longo = long day
• pessoa simpática = nice person

Putting the adjective before the noun (calma música) is possible but unusual and would sound poetic or highly marked, like in literature, song lyrics, or for special emphasis.

So for normal speech, música calma is the standard order.

Adjectives must agree in gender and number with the noun they describe.

• música is feminine singular (a música).
• So the adjective must also be feminine singular: calma.

Forms:

• Masculine singular: calmo
• Feminine singular: calma
• Masculine plural: calmos
• Feminine plural: calmas

Therefore:

• música calma (feminine singular)
• sons calmos (masculine plural)
  and not música calmo.

In European Portuguese, fones is an informal, very common word that means headphones or earphones/earbuds in general.

It’s short for fones de ouvido or related expressions.

More formal terms:

• auscultadores – standard word for headphones/earphones in Portugal (used in manuals, shops, etc.).
• auriculares – also used, especially for smaller earphones/earbuds.

In everyday speech in Portugal, people very often just say os fones.

Nos here is the contraction of:

• em (in / on) + os (the – masculine plural)
  = nos (“in/on the”).

So:

• nos fones = “on the headphones” / “in the headphones”

Similar contractions:

• em + a = na (na mesa – on the table)
• em + o = no (no carro – in the car)
• em + os = nos (nos fones – in/on the headphones)
• em + as = nas (nas ruas – in the streets)

You could also say nos meus fones = “in my headphones” if you want to add “my” explicitly.

Portuguese, like English, can sometimes leave the object or complement implied from context.

Começo devagar literally is “I start slowly,” and the listener understands “start (doing whatever we were talking about) slowly”:

• Start working
• Start running
• Start moving
• Start the task, etc.

The full version could be something like:

• …e começo a trabalhar devagar.
• …e começo a correr devagar.

But it’s very natural to omit that when the activity is clear from context. The sentence just describes the manner of beginning: slowly.

Yes, devagar is an adverb here, meaning slowly.

As an adverb, devagar is invariable: it does not change for gender or number:

• Falo devagar. – I speak slowly.
• Eles andam devagar. – They walk slowly.
• O carro vai devagar. – The car goes slowly.

You never say devagara, devagaras, etc. The form devagarinho also exists and means “very slowly / gently” and is also invariable.

In Portuguese, the present simple is often used to express general habits or repeated situations, just like in English:

• Quando estou desmotivado, ponho música calma…
  = “When I am demotivated, I put on calm music…”

This means “whenever that situation happens”, not just right now.

You could change the nuance with other verbs:

• Quando fico desmotivado… – “When I get/become demotivated…” (focus on the change into that state)
• Quando estou desmotivado, vou pôr música calma… – “When I’m demotivated, I’m going to put on calm music” (future intention in a specific scenario)

But for a general routine, the present is the most natural choice.

Overall, the sentence is neutral to informal, very natural in everyday speech:

• Quando estou desmotivado – neutral.
• ponho música calma – neutral/colloquial.
• nos fones – slightly informal, everyday word for headphones.

If you wanted it slightly more formal, you might say:

• Quando estou desmotivado, ponho música calma nos auscultadores e começo devagar.

But in normal conversation, the original sentence sounds perfectly natural and appropriate.