Eu estudo português no parque quando o tempo está bom.

Yes, you can often omit eu because Portuguese verb endings usually show the subject:

• (Eu) estudo português... = I study Portuguese... You keep eu for emphasis/contrast (e.g., Eu estudo, mas ele não) or for clarity in some contexts.

Estudo is the present tense of estudar. In Brazilian Portuguese, the present can cover:

• habitual/general: I study Portuguese (regularly)
• right now (depending on context): I’m studying Portuguese If you want to be explicitly “right now,” Brazilian Portuguese often uses estar + gerúndio:
• Eu estou estudando português... = I’m studying Portuguese (right now).

Both exist, but they’re used differently:

• Estudo português. = very common; “I study Portuguese” (language as a subject)
• Estudo o português. = also possible; can sound a bit more “the Portuguese language”/more specific or formal in some contexts
  In everyday Brazilian Portuguese, without the article is very common with languages after verbs like estudar, falar, aprender.

No is a contraction of em + o:

• em o parque → no parque = “in/at the park” Portuguese commonly contracts em with articles:
• em + a = na
• em + os = nos
• em + as = nas You can’t normally say em o parque in standard Portuguese.

Portuguese often uses:

• ser (é) for more permanent/characteristic qualities
• estar (está) for temporary states/conditions Weather is treated as a condition/state, so:
• quando o tempo está bom = “when the weather is nice/good (at that time)” O tempo é bom would sound more like “the climate is good” (a general trait of a place/season).

O tempo can mean both time and weather, but in this structure:

• o tempo está bom clearly means the weather is good To talk about “time” you’d usually see other cues, like tempo with amounts (muito tempo, pouco tempo) or expressions like tempo livre.

Portuguese commonly uses definite articles with general nouns:

• o tempo = “the weather” (in general/that day’s weather) It’s the normal, idiomatic way to refer to weather conditions.

Adjectives agree with the noun’s gender/number. Tempo is masculine singular, so:

• o tempo está bom (masc. sing.) If the noun were feminine, you’d use boa:
• a temperatura está boa (“the temperature is good”)

Usually no comma is needed when the quando clause comes after the main clause:

• Eu estudo português no parque quando o tempo está bom. A comma is more common when the subordinate clause comes first:
• Quando o tempo está bom, eu estudo português no parque.

Approximate (Brazilian) pronunciation cues:

• português: por-too-GES (stress on the last syllable; ê is a close “eh” sound)
• parque: PAR-kee (the r is often a light/hushed sound depending on region; final e is like “ee”)
• está: ess-TA (final á is open “ah,” stress on the last syllable)