Im Hochstuhl sitzt unsere Tochter gern, wenn sie ihren Brei isst.

German often puts the most important or most topical information first. Here, Im Hochstuhl is placed at the beginning to emphasize where the daughter likes to sit.

Because German is a verb-second language in main clauses, the finite verb still has to come in the second position:

• Im Hochstuhl | sitzt | unsere Tochter gern ...

So even though the subject unsere Tochter comes after the verb, the sentence is completely normal and grammatical.

A more neutral version would be:

• Unsere Tochter sitzt gern im Hochstuhl, wenn sie ihren Brei isst.

That version puts the subject first and sounds a bit more straightforward.

Im is a contraction of:

• in dem → im

So:

• im Hochstuhl = in the high chair

This contraction is very common in German.

Here, im Hochstuhl uses the dative case because it describes a location: the daughter is sitting in the high chair.

German often follows this pattern with two-way prepositions like in:

• Dative for location: where something is
  
  • im Hochstuhl sitzen
• Accusative for direction/movement toward a place: where something is going
  
  • in den Hochstuhl setzen = to put someone into the high chair

So:

• Sie sitzt im Hochstuhl. = She is sitting in the high chair.
• Ich setze sie in den Hochstuhl. = I put her into the high chair.

Der Hochstuhl means high chair, the kind small children sit in while eating.

It is a masculine noun, which matters for the article:

• der Hochstuhl
• im Hochstuhl = in dem Hochstuhl

Gern means gladly, with pleasure, or more naturally in English here, likes to.

So:

• Unsere Tochter sitzt gern im Hochstuhl
  means roughly
  Our daughter likes sitting in the high chair
  or
  Our daughter gladly sits in the high chair

German often uses gern where English uses like to.

For example:

• Ich esse gern Brei. = I like eating porridge.
• Sie sitzt gern dort. = She likes sitting there.

In German main clauses, adverbs like gern are often placed after the conjugated verb and before other elements, though word order can vary depending on emphasis.

Here:

• sitzt unsere Tochter gern

This is a natural position for gern.

If the sentence began with the subject, you would also commonly see:

• Unsere Tochter sitzt gern im Hochstuhl.

So gern is closely tied to the verb and tells you how she feels about the action: she likes doing it.

Because wenn sie ihren Brei isst is a subordinate clause, and German separates subordinate clauses with a comma.

So the structure is:

• Main clause: Im Hochstuhl sitzt unsere Tochter gern
• Subordinate clause: wenn sie ihren Brei isst

In German, this comma is required.

Because wenn introduces a subordinate clause, and in German subordinate clauses the conjugated verb usually goes to the end.

So:

• wenn
  • subject + object + verb
• wenn sie ihren Brei isst

Compare:

• Sie isst ihren Brei. → main clause, verb in second position
• ..., wenn sie ihren Brei isst. → subordinate clause, verb at the end

This is one of the most important word-order patterns in German.

Here wenn means when in the sense of whenever or if/when.

In this sentence, it suggests a repeated or general situation:

• She likes sitting in the high chair when/whenever she eats her porridge.

This is different from als, which is used for a single event in the past.

For example:

• Wenn sie Brei isst, sitzt sie gern im Hochstuhl. = Whenever she eats porridge, she likes sitting in the high chair.
• Als sie klein war, saß sie im Hochstuhl. = When she was little, she sat in the high chair.

Ihren Brei is in the accusative case because it is the direct object of isst.

The noun is:

• der Brei = porridge / mash

Masculine nouns change in the accusative:

• der Brei → den Brei

But because there is a possessive determiner, you get:

• ihr Brei = her porridge
• ihren Brei = her porridge, in the accusative masculine

So:

• sie isst ihren Brei = she eats her porridge

It could theoretically mean either in German, but here it clearly means she.

Why?

• The context is unsere Tochter = our daughter
• The verb is isst, which is singular
• They eat would be sie essen, not sie isst

So in this sentence, sie can only mean she.

Yes, absolutely. That is a very natural sentence.

Compare the two:

• Im Hochstuhl sitzt unsere Tochter gern, wenn sie ihren Brei isst.
• Unsere Tochter sitzt gern im Hochstuhl, wenn sie ihren Brei isst.

The difference is mainly focus:

• Starting with Im Hochstuhl highlights the place.
• Starting with Unsere Tochter is more neutral and straightforward.

Both are correct.

Most naturally, it sounds like a general habit or usual behavior.

German present tense often covers both:

• what is happening now
• what usually happens

Here, because of gern and wenn, the sentence strongly suggests a repeated situation:

• she generally likes sitting in the high chair when she eats her porridge

So it is best understood as a habitual statement.