S obzirom na to da nemamo puno vremena, kolač ćemo peći u malom kalupu.

It is a fixed expression meaning considering that, given that, or in view of the fact that.

A more literal breakdown is:

• s obzirom = with regard / in consideration
• na to = to that
• da = that

So the whole phrase is something like with regard to the fact that..., but in natural English you would usually translate it as considering that... or since....

It is very common and fairly neutral in style.

Croatian has two forms of this preposition: s and sa.

• s is the basic form
• sa is used when pronunciation would otherwise be awkward, especially before some consonants or clusters

Since obzirom begins with a vowel sound, s obzirom is the normal form.

So:

• s obzirom = correct
• sa obzirom = not standard here

That is because the standard Croatian structure is:

• s obzirom na to da + clause

The to points forward to the clause introduced by da.

So the pattern is not random; it is a set phrase. Native speakers often treat it as one chunk.

You may also hear s obzirom da in everyday speech, but s obzirom na to da is the more standard and careful form.

In Croatian, the negative particle ne is usually written together with the present-tense verb.

So:

• imamo = we have
• nemamo = we do not have

That is the normal spelling.

This is different from English, where negation usually uses a separate word like do not.

After quantity words like puno, the following noun is usually in the genitive.

So:

• puno vremena = a lot of time
• mnogo vremena = a lot of time
• malo vremena = little time
• dovoljno vremena = enough time

Here:

• dictionary form: vrijeme = time
• genitive singular: vremena

Because time is treated as an uncountable noun here, Croatian uses the genitive after puno.

Kolač is the direct object of peći, so it is in the accusative.

However, kolač is a masculine inanimate noun, and for many masculine inanimate nouns:

• nominative singular = accusative singular

So:

• nominative: kolač
• accusative: kolač

That is why the form looks unchanged.

Compare that with a masculine animate noun:

• pas = dog
• accusative: psa

So the lack of visible change here is normal.

Croatian future tense here is formed with:

• the auxiliary htjeti in a clitic form: ću, ćeš, će, ćemo, ćete, će
• plus the infinitive: peći

So:

• ćemo peći = we will bake

As for word order, ćemo is a clitic, and clitics usually go in the second position of the clause.

That is why Croatian can say:

• Kolač ćemo peći u malom kalupu.

Here kolač comes first, and ćemo follows it.

A different but also natural order would be:

• Peći ćemo kolač u malom kalupu.

The choice depends on emphasis and information structure. In your sentence, putting kolač first gives it a bit more prominence.

Yes, that is a very good question.

• peći is generally imperfective: to bake / be baking
• ispeći is generally perfective: to bake completely / finish baking

In this sentence, peći presents the activity more neutrally as a process.

If you said:

• kolač ćemo ispeći u malom kalupu

that would put more emphasis on the cake being successfully baked through / completed.

In real usage, both can be possible depending on what the speaker wants to highlight:

• peći = the action/process
• ispeći = the completed result

Because u can take two different cases depending on meaning:

• u + accusative = motion into
• u + locative = location in

Here the cake is being baked in a small pan/tin, so this is location, not movement.

That is why Croatian uses the locative:

• u malom kalupu = in a small pan/tin

If you were talking about putting the batter into the pan, then you would use accusative:

• Stavit ćemo smjesu u mali kalup. = We will put the batter into a small pan.

Because adjectives must agree with the nouns they describe in:

• gender
• number
• case

Here:

• kalup is masculine singular
• after u with location, it becomes locative singular: kalupu
• the adjective mali must match it, so it becomes malom

So:

• mali kalup = nominative
• u malom kalupu = locative

This kind of agreement is one of the most important patterns in Croatian grammar.

The comma separates the introductory subordinate clause from the main clause.

Structure:

• S obzirom na to da nemamo puno vremena, = subordinate clause
• kolač ćemo peći u malom kalupu. = main clause

Croatian normally uses a comma here, just as English would in a sentence like:

• Considering that we don't have much time, we will bake the cake in a small pan.

Because Croatian does not have articles like English the and a/an.

So:

• kolač can mean cake, a cake, or the cake
• u malom kalupu can mean in a small pan or, depending on context, in the small pan

The exact meaning comes from context, not from an article.

That is why English speakers often feel that Croatian is being less explicit, but for native speakers the meaning is usually clear from the situation.