У моей сестры маленький малыш, и утром она ставит коляску у подъезда.

Russian very often expresses possession with the pattern у + genitive + есть / implied “there is”.

So:

• У моей сестры маленький малыш literally means something like By my sister, there is a small baby
• Natural English translation: My sister has a little baby

This is much more normal in Russian than using иметь for everyday possession.

A few comparisons:

• У меня есть машина. = I have a car.
• У него есть брат. = He has a brother.

In your sentence, есть is omitted, which is very common in the present tense:

• У моей сестры маленький малыш. = My sister has a little baby.

Because у requires the genitive case, and both the adjective/pronoun and the noun have to agree.

Base forms:

• моя сестра = my sister

After у, they become genitive:

• моей сестры

So:

• моя → моей
• сестра → сестры

This is normal adjective/pronoun + noun agreement in Russian.

Yes, малыш already suggests a very young child, so маленький малыш can sound a bit repetitive if you analyze it literally.

But Russian does use combinations like this for emphasis, affection, or to stress how tiny/young the child is. It can feel like:

• a very little baby
• a tiny little one

So it is understandable and possible, even if slightly repetitive.

Depending on context, speakers might also say simply:

• У моей сестры малыш.
• У моей сестры маленький ребёнок.

Утром is the instrumental case of утро.

Russian often uses instrumental forms of parts of the day to mean at/in that time:

• утром = in the morning
• днём = in the daytime / during the day
• вечером = in the evening
• ночью = at night

So утром она ставит коляску... means:

• In the morning she puts/places the stroller...
• or, in a habitual sense, She puts the stroller... in the mornings

Ставит is imperfective, and here it suggests a repeated, habitual action or a general present-time description.

So:

• она ставит коляску у подъезда = she puts/parks the stroller by the entrance / she usually does this

If you used поставит, that would be perfective future:

• она поставит коляску = she will put the stroller down

If you wanted a one-time past action:

• она поставила коляску = she put the stroller down

So ставит fits well if the sentence describes a regular routine.

Usually it means a habitual or regular action.

In this sentence:

• У моей сестры маленький малыш, и утром она ставит коляску у подъезда.

the most natural reading is:

• My sister has a little baby, and in the morning she puts/parks the stroller by the entrance

This sounds like part of her normal routine.

Russian present tense can also describe something happening right now, but with утром and this kind of statement, the habitual meaning is the more likely one.

Because коляску is the accusative case, used here for the direct object of ставит.

Base form:

• коляска = stroller / pram / baby carriage

As a direct object:

• она ставит коляску = she puts the stroller

For feminine nouns ending in -а, accusative singular usually changes -а to -у:

• книга → книгу
• машина → машину
• коляска → коляску

Russian distinguishes between placing something upright / setting it somewhere and laying something down.

• ставить = to put / set / place upright
• класть = to lay / put down horizontally

A stroller normally stands on its wheels, so ставить коляску is the natural verb.

Examples:

• ставить бутылку на стол = to set a bottle on the table
• класть книгу на стол = to lay a book on the table

So here ставит коляску means puts/parks the stroller.

After the preposition у meaning by / near / next to, Russian uses the genitive case.

So:

• подъезд = entrance
• у подъезда = by the entrance / near the entrance

That is why подъезд becomes подъезда.

Compare:

• у дома = by the house
• у окна = by the window
• у подъезда = by the entrance

Подъезд often means the entrance to an apartment building, and by extension the entryway/stairwell section connected to that entrance.

In many Russian-speaking contexts, especially with apartment blocks, у подъезда means:

• by the building entrance
• outside the entrance
• near the entrance door of the apartment block

So it is more specific than just a generic doorway.

Yes, Russian often drops subject pronouns when the verb already makes the subject clear.

So you could hear:

• ...и утром ставит коляску у подъезда.

However, она is perfectly natural here and can help with clarity. In this sentence, there are several nouns nearby:

• сестры
• малыш
• коляску

Using она makes it immediately clear that the sister is the one doing the action, not someone else.

So the pronoun is optional in some contexts, but useful and natural here.

By itself, утром simply means in the morning. The exact meaning depends on context.

In this sentence, because the verb is ставит (imperfective present), the phrase most naturally suggests a repeated or usual action:

• in the morning / in the mornings
• effectively, every morning or as part of her morning routine

If the speaker wanted to describe one specific morning in the past, Russian would normally use past tense and context would make that clear:

• Утром она поставила коляску у подъезда. = In the morning / That morning she put the stroller by the entrance.

Yes, that is very normal.

In present-tense possession sentences, Russian often omits есть:

• У меня есть брат.
• У меня брат.

Both can be possible, but they are used a bit differently depending on style and emphasis.

In your sentence:

• У моей сестры маленький малыш

sounds natural as a simple statement of possession/existence.

If you add есть:

• У моей сестры есть маленький малыш

it is still understandable, but it may sound more explicit or stylistically different. In many everyday contexts, omission is the more natural choice.

Russian word order is flexible, but the given order is natural and neutral.

Current sentence:

• У моей сестры маленький малыш, и утром она ставит коляску у подъезда.

This flows as:

1. possession/topic: My sister has a little baby
2. routine action: and in the morning she puts the stroller by the entrance

Other orders are possible, but they would shift emphasis. For example:

• Утром она ставит коляску у подъезда.
  Neutral, with time first for framing.

• Коляску она ставит у подъезда утром.
  Stronger emphasis on the stroller.

• Она утром ставит коляску у подъезда.
  Slightly more focus on she.

So the original sentence is a good standard word order for learners.