Ne volim ići kroz park kad je mrak.

Croatian often leaves out subject pronouns because the verb ending already tells you who the subject is.

• volim = I like / I love
• so ja is not needed

You could say Ja ne volim ići kroz park kad je mrak, but that sounds more emphatic, like I don’t like it.

Negation is usually made by putting ne before the verb.

• volim = I like
• ne volim = I do not like / I don’t like

This is very common and straightforward in Croatian:

• znam = I know
• ne znam = I don’t know

After verbs like voljeti (to like/love), Croatian commonly uses the infinitive to express liking to do something.

So:

• volim ići = I like to go / I like going

This works much like English:

• Volim čitati. = I like reading / I like to read.
• Volim plivati. = I like swimming / I like to swim.

In standard Croatian, volim ići is the more natural and preferred structure.

• volim ići = standard Croatian
• volim da idem may be heard in some varieties of the wider BCMS area, but it is less standard in Croatian

So if you are learning Croatian specifically, volim ići is the form to aim for.

Not necessarily. Ići means to go, and in this sentence it refers generally to going through the park.

Depending on context, English might translate it as:

• to go through the park
• to walk through the park

If you wanted to be more specifically about walking, you could use hodati in some contexts, but ići is very natural here.

Because kroz takes the accusative case.

The noun park is masculine singular and inanimate, and for that type of noun the accusative singular looks the same as the nominative:

• nominative: park
• accusative: park

So:

• kroz park = through the park

If it were a noun with a different accusative ending, you would see the change more clearly.

Kroz means through.

It suggests movement from one side or part of something to another, passing inside or across it.

So:

• ići kroz park = to go through the park

A few useful comparisons:

• u park = into the park
• u parku = in the park
• kroz park = through the park

Croatian can express this idea in more than one way.

In your sentence:

• kad je mrak literally means something like when there is darkness or when it is dark

Here mrak is a noun meaning darkness.

A very common alternative is:

• kad je mračno = when it is dark

Both are natural.
Kad je mrak can feel slightly more like when it’s dark / when night has fallen, while kad je mračno is more directly adjectival/predicative: when it is dark.

Je is the 3rd person singular present form of biti (to be), meaning is.

So:

• kad = when
• je = is
• mrak = darkness

Literally, the structure is when darkness is, but in natural English we say when it’s dark.

Croatian does not need a dummy subject like English it in expressions like this.

Yes. Croatian word order is flexible.

These are both natural:

• Ne volim ići kroz park kad je mrak.
• Kad je mrak, ne volim ići kroz park.

The meaning stays basically the same. The version with Kad je mrak first gives a little more focus to the time condition.

Not always. Voljeti can mean both to love and to like, depending on context.

In this sentence:

• Ne volim ići kroz park... means I don’t like going through the park...

It does not mean something dramatic like I hate going through the park, unless the context makes it stronger.

Yes, that is a very natural translation depending on context.

• kad je mrak = when it’s dark
• in many situations, that is effectively at night or after dark

So possible English renderings include:

• I don’t like going through the park when it’s dark.
• I don’t like walking through the park after dark.
• I don’t like going through the park at night.

All of these capture the idea well.