Learn Hardcore Russian: Я собираюсь гулять в парке утром. - I am going to walk in the park in the morning.

Я буду гулять... = I will walk... (neutral, simple future, just a statement of a future action).
Я собираюсь гулять... = I am going to walk / I am planning to walk... (emphasizes intention or plan).

So собираюсь adds the nuance that you have a plan or intention, not just a neutral future event.

Why is гулять in the infinitive form and not conjugated, like гуляю?

After собираться (to be going to / to intend), Russian uses the infinitive:

Я собираюсь гулять. = I’m going to walk / I intend to walk.

This is similar to English want to do, plan to do, like to do, where the second verb is in the infinitive (to do). In Russian:

Я хочу гулять. – I want to walk.
Я люблю гулять. – I like to walk.
Я буду гулять. – I will walk.
Я собираюсь гулять. – I am going to walk / I intend to walk.

So гулять must stay in the infinitive here.

Why is гулять (imperfective) used here and not a perfective verb like погулять?

Imperfective гулять focuses on the process or duration of the action: to be walking / to go for a walk (as an activity).

Perfective погулять focuses on the completed action: to (have) a walk, to walk for a while and finish.

In Я собираюсь гулять в парке утром, the speaker is talking about the activity planned for the morning, not emphasizing that the walk will be completed. So the imperfective is more natural.

If you say:

Я собираюсь погулять в парке утром.
This can sound more like: I’m planning to go have a (one-time, complete) walk in the park in the morning.

Both are possible, but гулять is the neutral way to name the activity.

What is the literal meaning and function of собираться here? It looks like a reflexive verb.

Собираться is the reflexive form of собирать (to gather, collect). Literally, собираться can mean to gather oneself, to congregate, to get ready, or to intend.

Meanings of собираться include:

to get ready:
- Я собираюсь на работу. – I’m getting ready for work.
to be about to / to intend / to be going to (with an infinitive):
- Я собираюсь гулять. – I’m going to walk / I intend to walk.
to gather (people):
- Мы собираемся у меня дома. – We are gathering at my place.

In your sentence it has meaning 2: I intend / I am going to. The reflexive ending -сь is just part of the verb’s normal form; it doesn’t mean “myself” in a direct, literal way here.

Why does the sentence start with Я? Could it be omitted?

You can say:

Я собираюсь гулять в парке утром.
Собираюсь гулять в парке утром.

Both are grammatically correct.

Russian often drops subject pronouns when the subject is clear from the verb ending. Собираюсь in the 1st person singular makes it clear that the subject is я.

Including Я:

is a bit more explicit and neutral,
is good for beginners,
can also be used for emphasis (for example, contrasting with someone else: Я собираюсь гулять, а он — работать.)

Omitting Я is common in speech and sounds natural and slightly more informal.

Why is it в парке and not в парк?

В парк (accusative) usually answers куда? – where to?, i.e. direction:

Я иду в парк. – I’m going to the park.

В парке (prepositional) answers где? – where?, i.e. location:

Я гуляю в парке. – I walk in the park.

In Я собираюсь гулять в парке утром, the focus is where the walking will take place (location), so в парке (prepositional) is correct.

Why is it в парке and not на парке?

With парк, Russian almost always uses в, not на, because a park is treated as a closed or bounded space you are inside of:

в парке, в лесу, в доме, в магазине, в школе.

На is used with open surfaces or certain institutions/places by idiom:

на улице – in the street
на море – at the seaside
на стадионе – at the stadium
на работе – at work
на кухне – in the kitchen

So by standard usage it is в парке – in the park.

What case is в парке and how is парк declined there?

В парке is in the prepositional case (also called locative) after the preposition в meaning in (location).

The noun парк is masculine, singular:

Nominative (dictionary form): парк – (a) park
Prepositional (after в, о, etc., for location/topic): в парке – in the park, о парке – about the park

So парк → парке is the regular masculine prepositional ending -е.

What is утром exactly? Why not в утро?

Утром is the instrumental case of утро (morning), but in practice it functions adverbially and is best learned as a fixed time expression: in the morning.

Russian commonly uses the instrumental case without a preposition to express “in/at [time of day]”:

утром – in the morning
днём – in the daytime / in the afternoon
вечером – in the evening
ночью – at night

В утро for “in the morning” is not natural in modern Russian; you normally say утром.

Where can утром go in the sentence? Is the word order fixed?

Russian word order is flexible. All of these are possible and natural:

Я собираюсь гулять в парке утром.
Я утром собираюсь гулять в парке.
Утром я собираюсь гулять в парке.

They all mean essentially the same thing: I’m going to walk in the park in the morning.

Differences are mostly in emphasis and style:

Утром я собираюсь… – emphasizes in the morning.
Я собираюсь гулять в парке утром. – neutral, very typical order.
Я утром собираюсь… – emphasizes both I and in the morning, often contrastive (I, in the morning, am going to…, not at some other time).

Can Я собираюсь гулять в парке утром also mean “I’m going to go for a walk” (not just “I’m going to walk”)?

Yes. The verb гулять in Russian often corresponds to to go for a walk or to be out walking, not just the literal verb to walk (on foot).

So Я собираюсь гулять в парке утром is naturally understood as:

I’m going to go for a walk in the park in the morning.
or I plan to go walking in the park in the morning.

Context will clarify that it’s a leisure walk, not just moving on foot from A to B.

What is the difference between Я собираюсь гулять в парке утром and Я пойду гулять в парке утром?

Both refer to a future walk in the park, but they focus on different things:

Я собираюсь гулять в парке утром.
Emphasizes intention/plan. Literally: I am going to / I intend to walk in the park in the morning.
Я пойду гулять в парке утром.
Uses пойду (future, one-directional “to go on foot”), emphasizing the act of going to walk. Literally: I will go (on foot) to walk in the park in the morning.

In practice:

Use собираюсь when you’re talking about what you plan to do.
Use пойду when you’re emphasizing that you will go (there) at that time.

Is Я собираюсь гулять в парке утром formal or informal?

It is neutral and can be used in both informal and relatively formal contexts.

In casual conversation: perfectly natural.
In more formal speech or writing: still fine, but very formal contexts might prefer more neutral future forms without the “intention” nuance, e.g. Я буду гулять в парке утром or something more specific (буду заниматься спортом в парке утром, etc.).

For everyday spoken Russian, Я собираюсь гулять в парке утром sounds completely normal.