På morgonen lämnar hon barnet på förskolan och ställer barnvagnen i hallen.

This is because Swedish follows the V2 rule in main clauses: the finite verb must come in the second position.

So:

• Hon lämnar barnet ... = She drops off the child ...
• På morgonen lämnar hon barnet ... = In the morning, she drops off the child ...

When På morgonen is moved to the front, the verb lämnar still has to stay in second position, so the subject hon comes after it.

This is just the normal Swedish time expression. Swedish often uses på in expressions like:

• på morgonen = in the morning
• på kvällen = in the evening
• på natten = at night

So even though English uses in, Swedish uses på here.

In this kind of fixed time expression, Swedish usually uses the definite form:

• på morgonen = in the morning
• på eftermiddagen = in the afternoon
• på kvällen = in the evening

So morgonen does not necessarily mean the morning in a very specific sense here. It is simply the standard idiomatic form in Swedish.

Here, lämnar is best understood as drops off.

The verb lämna often means:

• to leave
• to hand over
• to drop off

In the phrase lämnar barnet på förskolan, it means that she takes the child to preschool and leaves the child there.

Swedish often uses the present tense for habitual or repeated actions, just like English can do:

• På morgonen lämnar hon barnet ...
  = In the morning she drops off the child ...

This sounds like part of a routine. It does not have to mean only right now; it can describe what she normally does.

Barnet is the definite form of barn and means the child.

Swedish uses the definite form when the listener is expected to know which person or thing is meant. In context, this is probably her child or a specific child already understood from the situation.

Compare:

• ett barn = a child
• barnet = the child

With schools and many institutions, Swedish often uses på where English might expect at or sometimes in.

So:

• på förskolan = at preschool
• på skolan = at school
• på jobbet = at work

This is a common Swedish preposition pattern and usually has to be learned as part of the expression.

Förskola is the Swedish word for preschool or daycare/preschool care, depending on context.

It refers to early childhood education and care before compulsory school. In everyday older or informal speech, some people also say dagis, but förskola is the standard and more official word.

Because both verbs have the same subject: hon.

Swedish, like English, often leaves out the repeated subject in coordinated clauses:

• På morgonen lämnar hon barnet på förskolan och ställer barnvagnen i hallen.

This works like English:

• In the morning she drops off the child at preschool and puts the stroller in the hall.

You could repeat hon, but it would usually sound unnecessary here.

Ställer comes from ställa, which often means to place something standing/upright.

Swedish commonly chooses different placement verbs depending on the position of the object:

• ställa = put something so that it stands
• lägga = lay/put something so that it lies flat
• sätta = set/place, often with seated position or in certain fixed expressions

A barnvagn is normally thought of as something that stands on its wheels, so ställer barnvagnen is the natural choice.

Both are definite because they refer to specific, understood things:

• barnvagnen = the stroller
• hallen = the hall / hallway

In context, this usually means:

• a particular stroller that belongs to the child/family
• a particular hall, probably the entrance hall in a home or building

Swedish uses the definite form a lot in cases where English might also say the.

Because hallen is treated as an enclosed space or room, so Swedish uses i = in.

• i hallen = in the hall / hallway

A simple way to think about it is:

• i is often used for being inside a room, building, container, or area
• på is often used for surfaces, institutions, or certain set expressions

So i hallen is the natural choice here.