Posle večere ćemo videti fotografije.

Because posle normally requires the genitive case in Serbian.

• večera = dinner
• večere = of dinner / after dinner, in the genitive singular

So posle večere literally follows the pattern after + genitive.

This is very common:

• posle škole = after school
• posle posla = after work
• posle ručka = after lunch

Večere is genitive singular of večera.

The noun večera is a feminine noun ending in -a, and many such nouns form the genitive singular with -e:

• žena → žene
• škola → škole
• večera → večere

In this sentence, the genitive is used because of the preposition posle.

Serbian often forms the future with:

present tense of hteti + infinitive

Here:

• ćemo = we will
• videti = to see

So:

• ćemo videti = we will see

This is the standard future tense, often called future I.

Full breakdown:

• ću = I will
• ćeš = you will
• će = he/she/it will
• ćemo = we will
• ćete = you plural / formal will
• će = they will

Both are possible in Serbian.

You can say:

• ćemo videti
• videćemo

Both mean the same thing: we will see.

The two-word version uses the auxiliary plus infinitive:

• ćemo videti

The one-word version attaches the future auxiliary to the verb form:

• videćemo

In many contexts, both are natural. Learners often first meet the two-word pattern because it is easier to analyze.

Because in Serbian the future auxiliary often comes before the infinitive in normal sentence structure:

• Mi ćemo videti fotografije.
• Sutra ću doći.
• Oni će kupiti hleb.

The auxiliary ću/ćeš/će/ćemo/ćete/će is a clitic, which means it tends to take a fixed position near the beginning of the clause, usually after the first stressed element.

That is why Serbian word order may look a little different from English.
For example:

• Posle večere ćemo videti fotografije.

Here ćemo comes after the first phrase Posle večere.

Videti means to see, while gledati means to watch / look at.

So the difference is similar to English:

• videti = to see
• gledati = to watch / to look at

In this sentence, videti fotografije suggests seeing the photos, having a look at them, or being shown them.
If you said gledati fotografije, that would sound more like looking at photos for some time, perhaps examining them.

Both can be possible in real life, but videti is perfectly natural here.

Fotografije is the accusative plural of fotografija.

Since videti is a transitive verb, it takes a direct object, and the direct object here is fotografije.

For feminine nouns ending in -a, the plural often looks like this:

• fotografija = photograph
• fotografije = photographs

In this case, nominative plural and accusative plural are the same:

• fotografije = photographs

So the form is exactly what you would expect for we will see photographs.

They are close in meaning, but not always identical in tone.

• fotografija = photograph, photo
• slika = picture, image, painting, and often also photo in everyday speech

In casual Serbian, people very often use slike for photos:

• Pogledaj slike. = Look at the photos/pictures.

Fotografije can sound a bit more precise or formal than slike, though both are common.

Yes, it matters. Videti is generally a perfective verb.

In Serbian, aspect is very important:

• perfective verbs present an action as complete or whole
• imperfective verbs present an action as ongoing, repeated, or in progress

Videti is commonly used for a completed act of seeing:

• Video sam ga. = I saw him.

In the future, perfective verbs are very common when talking about a single completed event:

• Posle večere ćemo videti fotografije.

That sounds like one future event: after dinner, we will see the photos.

Yes, absolutely.

Serbian often drops subject pronouns because the verb form already shows the person:

• ćemo already tells you the subject is we

So:

• Ćemo videti fotografije is not used by itself because the clitic needs a host, but
• Posle večere ćemo videti fotografije is fine
• Mi ćemo videti fotografije is also fine

Adding mi makes the subject more explicit, and it may add emphasis:

• Mi ćemo videti fotografije, a oni neće. = We will see the photos, but they won’t.

Yes. Serbian word order is more flexible than English, although not completely free.

Possible versions include:

• Posle večere ćemo videti fotografije.
• Fotografije ćemo videti posle večere.
• Mi ćemo posle večere videti fotografije.

The basic meaning stays the same, but the emphasis changes.

For example:

• Fotografije ćemo videti posle večere puts more focus on the photos
• Posle večere ćemo videti fotografije puts more focus on after dinner

One thing to remember is that the future auxiliary ćemo is a clitic, so it tends to stay in a position typical for clitics rather than just anywhere.

Ćemo is pronounced roughly like CHYEH-moh, but that is only an approximation.

A few important points:

• ć is a soft consonant, softer than English ch
• e is like e in met
• o is a clear short o

Also, Serbian spelling is very phonetic, so once you learn the sounds, pronunciation becomes much easier.

No. Another common form is poslije, especially in varieties of Serbian spoken in some regions and in closely related standards.

So you may see:

• Posle večere ćemo videti fotografije.
• Poslije večere ćemo videti fotografije.

Both mean the same thing.
Posle is very common in Serbian usage, especially in Serbia.

Not in this exact form.

English we’ll see often means we’ll find out later or it’s not decided yet. Serbian can express that idea, but not usually with videti fotografije, because here there is a clear direct object: photographs.

This sentence straightforwardly means that after dinner, the photos will be seen/viewed.

If you wanted the idiomatic English meaning we’ll see, Serbian would more naturally use:

• Videćemo.

That can mean:

• We’ll see
• We’ll find out
• It depends

But in your sentence, the meaning is concrete, not idiomatic.