Eu pedalo devagar no parque.

Portuguese is a “pro-drop” language, which means subject pronouns like eu are often optional because the verb ending already shows who is acting. You can perfectly say:
• Pedalo devagar no parque.
Omitting eu sounds more natural in everyday speech, but keeping it can add clarity or emphasize that you are the one pedaling.

Pedalo comes from the infinitive pedalar (“to pedal”) and is the first-person singular present indicative form. In other words, it literally means “I pedal” or “I am pedaling.” A quick conjugation of pedalar in the present is:
• eu pedalo
• tu pedalas
• ele/ela pedala
• nós pedalamos
• vós pedais
• eles/elas pedalam

In Portuguese, manner adverbs (how you do something) normally follow the verb:
• Pedalo devagar
However, you can place them at the start for stylistic emphasis:
• Devagar, eu pedalo no parque.
That inversion highlights the slowness as the main focus.

No = em + o. The preposition em means “in/at,” and o is the definite article for masculine singular nouns. Since parque is o parque, you combine them:
• em + o parque → no parque
If it were feminine (e.g. a praia), you’d say na praia.

Generally no. With concrete, countable places, Portuguese usually requires the definite article:
• Correct: no parque, na escola, no cinema
• Incorrect: em parque, em escola, em cinema
Omitting the article sounds ungrammatical in standard usage.

A very common synonym is andar de bicicleta. You could say:
• Eu ando de bicicleta devagar no parque.
It conveys the same meaning and is often preferred in casual conversation.