Do kina imamo otprilike deset minuta pješice, ako ne bude gužve na glavnoj ulici.

This is a very common Croatian pattern.

Imati can be used to talk about the amount of time or distance between where you are and a destination:

• Do škole imamo pet minuta. = We’re five minutes from the school.
• Do centra imamo deset minuta autom. = The city centre is ten minutes away by car / It takes us ten minutes by car.

So Do kina imamo otprilike deset minuta pješice literally means something like:

To the cinema, we have about ten minutes on foot.

Natural English usually changes the structure, but the Croatian sentence is perfectly normal.

Because do and u express slightly different ideas.

• u kino = to the cinema, with the idea of going into it
• do kina = up to the cinema / as far as the cinema

In this sentence, the speaker is talking about distance/time to reach the place, so Croatian typically uses do + genitive:

• Do kina imamo deset minuta.
• Do stanice je dvije minute.
• Do centra nije daleko.

If you were talking about the action of going there, u kino would be natural:

• Idemo u kino. = We’re going to the cinema.

So here do kina is the right choice because the sentence is about how far away the cinema is, not about the act of entering it.

Because do requires the genitive case.

The noun is:

• nominative: kino
• genitive: kina

So:

• kino = cinema (dictionary form)
• do kina = to the cinema / as far as the cinema

This is a standard pattern:

• do grada = to the city
• do škole = to the school
• do mora = to the sea

Because Croatian has no articles like a/an/the.

So glavna ulica can mean:

• a main street
• the main street

The exact meaning comes from context.

In this sentence, na glavnoj ulici is naturally understood as on the main street because the speaker probably has a specific street in mind that both speaker and listener know about.

This is something English speakers need to get used to: Croatian usually leaves definiteness unstated unless context makes it clear.

After numbers 5 and higher, Croatian normally uses the genitive plural of the noun.

So:

• jedna minuta
• dvije / tri / četiri minute
• pet minuta
• deset minuta

For minuta, the genitive plural happens to look the same as the basic singular form:

• nominative singular: minuta
• genitive plural: minuta

So deset minuta means ten minutes and is exactly what you should expect after deset.

Pješice means on foot or walking.

It is an adverb, so it does not change form.

Examples:

• Idemo pješice. = We’re going on foot.
• Do posla imam dvadeset minuta pješice. = My work is twenty minutes away on foot.

A related word you may also hear is pješke, which also means on foot. In many situations, the two are interchangeable.

Otprilike means approximately, about, or roughly.

Here it modifies deset minuta:

• otprilike deset minuta = about ten minutes

Its position is somewhat flexible:

• Do kina imamo otprilike deset minuta pješice.
• Do kina imamo deset minuta pješice, otprilike.

The version in your sentence is very natural.

Because this clause refers to a future condition: if there isn’t / if there won’t be traffic/congestion.

In Croatian, after ako (if), it is very common to use bude for this kind of future meaning:

• Ako bude vremena... = If there is / if there will be time...
• Ako ne bude kiše... = If there isn’t rain...
• Ako ne bude gužve... = If there isn’t congestion...

Why not the other forms?

• ako nije would usually sound like a present or past-state condition, not the normal future-looking condition here.
• ako neće biti is much less natural in this kind of sentence.

So ako ne bude is the standard and idiomatic choice.

Because with biti / imati in the sense of there is / there will be, Croatian often uses the genitive for indefinite amounts or occurrences.

So you get patterns like:

• Ima vremena. = There is time.
• Nema problema. = There is no problem / no problem.
• Bit će ljudi. = There will be people.
• Ne bude gužve. = There won’t be congestion / crowding.

Here:

• nominative: gužva
• genitive singular: gužve

So ako ne bude gužve is the normal form.

By contrast, if you made gužva the subject, you could say:

• Gužva je na glavnoj ulici. = There is congestion on the main street.

Both patterns exist, but this sentence uses the genitive/existential pattern.

Gužva can mean several related things:

• a crowd
• crowdedness
• congestion
• heavy traffic / a traffic jam, depending on context

In na glavnoj ulici, the most natural meaning is probably traffic/congestion or general busyness on the street.

So ako ne bude gužve na glavnoj ulici means something like:

• if there isn’t heavy traffic on the main street
• if the main street isn’t crowded/congested

It is in the locative singular.

That is because na can take different cases depending on meaning:

• na + locative = location (on / at)
• na + accusative = movement onto/toward

Here the meaning is location:

• na glavnoj ulici = on the main street

Forms:

• glavna ulica = nominative
• na glavnoj ulici = locative

So both words change:

• glavna → glavnoj
• ulica → ulici

Croatian word order is fairly flexible, so yes, you could say:

• Imamo do kina otprilike deset minuta pješice.

But the original:

• Do kina imamo otprilike deset minuta pješice...

sounds very natural because Do kina is placed first as the topic: as for the cinema / to the cinema.

Starting with the destination often feels smooth when you are talking about distance:

• Do škole imam pet minuta.
• Do posla imamo pola sata.
• Do kina imamo deset minuta.

So the original word order is not the only possible one, but it is very idiomatic.

Yes. A few natural alternatives are:

• Do kina nam treba otprilike deset minuta pješice, ako ne bude gužve na glavnoj ulici.
• Kino je otprilike deset minuta pješice odavde, ako ne bude gužve na glavnoj ulici.

These all express roughly the same idea, but with slightly different structures:

• imamo = we have ten minutes to the cinema
• nam treba = it takes us ten minutes
• je ... odavde = it is ten minutes away from here

Your original sentence is completely normal and idiomatic.