Kad budemo imali više vremena, napravit ćemo i kobasice za zimu.

Because Croatian normally uses the future II in subordinate clauses introduced by words like kad (when), ako (if), čim (as soon as), etc. when the whole sentence refers to the future.

So the pattern is:

• subordinate clause: kad budemo imali više vremena
• main clause: napravit ćemo i kobasice za zimu

In other words:

• budemo imali = future II
• napravit ćemo = future I

A native English speaker expects future in both clauses, but Croatian often does not do that in this structure.

Informally, you may sometimes hear kad ćemo imati, but the sentence you were given is the standard and better model to learn.

It is the future II of imati (to have).

It is formed with:

• the present tense of biti in the appropriate form
• plus the l-participle of the main verb

Here:

• budemo = we will be
• imali = participle of imati

So:

• budemo imali = when we have / when we will have

Even though imali may look past-like, it is not past here. It is just part of the future II construction.

Because the implied subject is we.

The participle in this construction agrees with the subject:

• ja budem imao / imala
• ti budeš imao / imala
• mi budemo imali / imale

In your sentence, the speaker is using the usual plural form imali. That is the standard default form for a mixed group or an unspecified group of we. If the speakers were all female, you could also hear budemo imale.

This is a standard spelling rule in Croatian future I.

When the auxiliary ću, ćeš, će, ćemo, ćete, će comes after the infinitive, the final -i of the infinitive drops in writing:

• napraviti + ćemo → napravit ćemo

Compare:

• Napravit ćemo kobasice.
• Kobasice ćemo napraviti.

Both are correct, but they are written differently because of word order:

• after the verb: napravit ćemo
• before the verb: ćemo napraviti

Here i means also / too.

So:

• napravit ćemo i kobasice za zimu

means something like:

• we’ll also make sausages for winter
• we’ll make sausages for winter too

It does not mean and here in the sense of joining two equal items. It adds the idea that sausages are one more thing they will make.

Because više (more) is followed by the genitive.

So:

• više vremena = more time

The noun vrijeme is neuter, and after više, it appears in the genitive singular:

• nominative: vrijeme
• genitive: vremena

This is a very common pattern in Croatian:

• puno vremena = a lot of time
• više novca = more money
• manje problema = fewer problems / less trouble

Here kobasice is in the accusative plural, because it is the direct object of napraviti (to make).

Base form:

• kobasica = sausage

In this sentence:

• napravit ćemo kobasice = we will make sausages

For this noun, the accusative plural looks the same as the nominative plural:

• nominative plural: kobasice
• accusative plural: kobasice

So the form itself does not change, but its function does.

Literally, it means for winter.

This is a very natural expression in Croatian and other South Slavic languages. It often refers to food being made, stored, preserved, or prepared for the winter season.

So kobasice za zimu suggests sausages intended to be kept or used during winter.

Also, za here takes the accusative:

• zima = winter
• za zimu = for winter

Because Croatian often leaves subject pronouns out when they are already clear from the verb form.

Here the verbs already show we:

• budemo imali = we will have
• napravit ćemo = we will make

So adding mi is usually unnecessary unless you want emphasis or contrast.

For example:

• Kad budemo imali više vremena, napravit ćemo i kobasice za zimu.
  Neutral, normal.

• Kad budemo imali više vremena, mi ćemo napraviti i kobasice za zimu.
  More emphatic: we will do it.

Yes. Croatian word order is fairly flexible, although not completely free.

Your sentence is a natural, neutral version:

• Kad budemo imali više vremena, napravit ćemo i kobasice za zimu.

But other versions are possible, depending on emphasis:

• Kad budemo imali više vremena, i kobasice ćemo napraviti za zimu.
• Kad budemo imali više vremena, kobasice ćemo napraviti i za zimu.

The meaning stays close, but the focus shifts slightly. The original sentence sounds very natural and is a good model to copy.

Not always, but very often when the clause refers to a future situation.

Compare:

• Kad imam vremena, kuham.
  When I have time, I cook.
  (general/habitual present)

• Kad budemo imali više vremena, napravit ćemo kobasice.
  When we have more time, we’ll make sausages.
  (specific future situation)

So the choice depends on whether you are talking about:

• a general fact or habit → present tense
• a future event in a subordinate clause → often future II

Not exactly.

• raditi usually means to do / to work / to be making
• napraviti usually means to make / to do, and complete it

In this sentence, napraviti kobasice sounds right because it means to make / prepare sausages as a completed action.

So napravit ćemo gives the idea:

• we’ll make them
• we’ll get them done

That completed sense is why napraviti fits well here.