Малыш любит засыпать, когда коляска медленно катится по тихой улице.

Because любит usually describes something someone enjoys doing in general, not one single completed event.

• засыпать is imperfective, so it works well for a repeated or habitual action: likes falling asleep / likes drifting off
• уснуть is perfective, so it points to one completed result: to fall asleep successfully, once

So любит засыпать sounds natural for a baby’s usual habit. Любит уснуть would sound much less natural here.

Yes, here it means to fall asleep.

Russian has two different verbs that look the same in writing:

• засыпа́ть = to fall asleep
• засы́пать = to cover, fill up, pour over

The meaning is clear from context here: a baby and a stroller strongly suggest falling asleep, not covering something up.

Because катиться is the intransitive/reflexive verb: to roll, to be rolling, to move on wheels.

Compare:

• катить коляску = to roll/push the stroller
• коляска катится = the stroller is rolling / moving along

So in this sentence, the stroller itself is the subject, which is why Russian uses катится.

Not necessarily.

In Russian, катиться focuses on the stroller’s motion as something rolling along. It does not have to mean nobody is pushing it. In this sentence, it simply describes the stroller moving smoothly along the street, most likely while someone is pushing it.

It is dative case.

After по in the sense of along / through / over, Russian usually uses the dative:

• по улице = along the street
• по тихой улице = along the quiet street

Both words are feminine singular dative:

• тихой
• улице

So the endings are there because of по.

They mean different things:

• по тихой улице = along the quiet street → movement along it
• на тихой улице = on the quiet street → location, being there

In this sentence the stroller is moving, so по is the natural choice.

Because it describes how the stroller is moving, so Russian needs an adverb.

• медленный = slow (adjective, describes a noun)
• медленно = slowly (adverb, describes a verb)

Here it modifies катится, so медленно is correct: rolls slowly / moves slowly.

It can be understood as when, but in this sentence it has a general, habitual sense close to whenever.

That is because the whole sentence describes a typical situation:

• Малыш любит засыпать... = this is something the baby generally likes to do
• когда коляска медленно катится... = in the situation when/whenever the stroller is moving slowly

So in natural English, when or whenever could both fit depending on style.

Because Russian uses the present tense for habitual or repeated actions, just like English can.

• любит = likes
• катится = is rolling / rolls

Russian does not need a special tense here. The present tense is enough to show a general pattern: the baby likes falling asleep when the stroller moves slowly along the street.

Yes.

In Russian, a subordinate clause introduced by когда is normally separated by a comma:

• Малыш любит засыпать, когда коляска медленно катится по тихой улице.

So the comma here is standard punctuation.

Yes, Russian word order is flexible.

For example, you could also say:

• Когда коляска медленно катится по тихой улице, малыш любит засыпать.

That still means the same thing overall. The original version is very natural and neutral. Changing the order mostly changes what comes first in the speaker’s focus, not the basic meaning.

Малыш is a common, warm, everyday word for a little child, often a baby or toddler.

It is slightly affectionate and feels natural in family contexts. Depending on context, it can mean:

• baby
• little one
• toddler
• small child

So it is not a highly technical word like infant. It sounds natural and human.

Here коляска means a baby stroller / pram / pushchair.

It is a general word for a wheeled vehicle for a baby or small child. The exact English word depends on dialect and context, but in this sentence it clearly refers to the child’s stroller.