Gledam mapu, jer ne znam gde je stanica.

Serbian often omits subject pronouns when they are already clear from the verb form.

• gledam = I look / I am looking
• znam = I know

The ending -am in gledam and the form znam already show first person singular, so ja is not necessary.

You could say Ja gledam mapu..., but that usually adds emphasis, like I’m the one looking at the map.

Because mapu is the accusative singular form of mapa.

• mapa = nominative, the basic dictionary form
• mapu = accusative, used here because it is the direct object of gledam

So:

• Mapa je na stolu. = The map is on the table.
• Gledam mapu. = I’m looking at the map.

For many feminine nouns ending in -a, the accusative singular ends in -u.

Because Serbian often uses the verb gledati with a direct object, where English uses look at.

So English:

• I’m looking at a map

becomes Serbian:

• Gledam mapu

Serbian does not need a separate word corresponding to English at here.

Jer means because.

So:

• Gledam mapu, jer ne znam gde je stanica. = I’m looking at the map because I don’t know where the station is.

A common alternative is zato što:

• Gledam mapu zato što ne znam gde je stanica.

Both are correct. Jer is shorter and very common in everyday Serbian.

In standard Serbian, a comma is normally used before jer when it introduces a reason clause.

So this is standard:

• Gledam mapu, jer ne znam gde je stanica.

This works similarly to English, where a comma may appear before because in some sentence structures, but in Serbian the comma before jer is much more standard and expected.

Because the negative particle ne is usually written separately from verbs in Serbian.

So:

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

Other examples:

• radim → ne radim
• gledam → ne gledam

There are some important exceptions in Serbian, such as nisam and nemam, but with znam, the correct form is ne znam.

Because gde je stanica is the natural Serbian word order.

In Serbian, with gde (where), the verb usually comes right after it in this kind of clause:

• Gde je stanica? = Where is the station?
• Ne znam gde je stanica. = I don’t know where the station is.

The version gde stanica je sounds unnatural in standard Serbian.

Because stanica is the subject of the clause gde je stanica.

In that clause:

• gde = where
• je = is
• stanica = the station

Since stanica is the thing that is somewhere, it stays in the nominative singular:

• stanica = nominative

Compare:

• Stanica je blizu. = The station is near.
• Ne znam gde je stanica. = I don’t know where the station is.

Here, gde means where in the sense of location.

It asks about a place:

• Gde je stanica? = Where is the station?

But Serbian uses different words for some other English where ideas:

• gde = where, at what place
• kuda = which way, along what route
• odakle = from where
• dokle = up to where / how far

So gde is the right word here because the speaker wants to know the station’s location.

Yes. Gde and gdje are variant forms.

• gde is common in Ekavian Serbian
• gdje appears in Ijekavian varieties

They mean the same thing: where.

So depending on the variety, you may see:

• Ne znam gde je stanica.
• Ne znam gdje je stanica.

Both are correct in the appropriate regional/standard context.

It can mean both, depending on context.

Serbian present tense often covers both the English simple present and present continuous:

• gledam = I look / I am looking
• znam = I know

In this sentence, English naturally uses I’m looking at a map, because it describes what the speaker is doing right now.

Also, gledati is an imperfective verb, which fits an ongoing action well.

By itself, stanica is a general word meaning station or stop, and the exact meaning depends on context.

It can refer to things like:

• autobuska stanica = bus station
• železnička stanica = train station
• tramvajska stanica = tram stop

In this sentence, stanica is left general, so the meaning is simply the station / stop, whichever one the context makes clear.