Skulle ni kunna kontrollera tidtabellen innan vår avgång?

Because this is a yes/no question. In Swedish, the finite verb usually comes first in that kind of question.

• Statement: Ni skulle kunna kontrollera tidtabellen...
• Question: Skulle ni kunna kontrollera tidtabellen...?

So the word order is similar to English Would you be able to check the timetable...?

Together, skulle ni kunna makes the request sound polite and less direct.

• kunna = be able to / can
• skulle adds a conditional/polite tone, like would

So Skulle ni kunna... is roughly like:

• Would you be able to...
• Could you...

A more direct version would be Kan ni kontrollera tidtabellen? That is still correct, but less soft and polite.

Ni means you.

It can be:

• plural you: speaking to more than one person
• sometimes polite/formal singular you: speaking respectfully to one person

In modern Swedish, people often use du even in many polite situations, so ni can sound more formal, more customer-service-like, or sometimes a little stiff depending on context. But it is absolutely understandable and correct.

Because after modal verbs like skulle and kunna, Swedish normally uses the next verb in the infinitive without att.

So:

• skulle
• kunna
• kontrollera

This is similar to English:

• would be able to check

You do not say skulle ni kunna att kontrollera.

Tidtabellen is the definite form of tidtabell, meaning the timetable.

It breaks down like this:

• tidtabell = timetable
• tidtabellen = the timetable

In Swedish, the definite article is often added as a suffix to the noun instead of using a separate word like the.

Also, tidtabell is a compound noun:

• tid = time
• tabell = table/chart

So literally it is something like a time-table.

Because after a possessive like min, din, vår, er, deras, Swedish usually uses the noun in its indefinite form.

So:

• vår avgång = our departure
• not vår avgången

Compare:

• min bok = my book
• hennes bil = her car
• vårt hus = our house

The possessive already makes the noun specific, so Swedish does not usually add the definite ending too.

Avgång means departure, especially in contexts involving scheduled transport:

• train departure
• flight departure
• ferry departure

That makes it a very natural word in a sentence about checking a timetable.

A related word is avresa, which also means departure/journey start, but avgång fits especially well when you are thinking about a scheduled leaving time.

Innan means before.

In this sentence, innan vår avgång means before our departure.

You may also see före in similar contexts, and in many situations both can work. Very roughly:

• innan is often common before a clause or an event
• före is often common before a noun phrase

But real usage overlaps a lot, and native speakers may accept both in many cases.

So innan vår avgång is fine and understandable.
A version with före vår avgång would also be possible in many contexts.

It is natural, but it sounds a bit formal or careful.

Kontrollera means check / verify / inspect. In everyday spoken Swedish, people might also say:

• kolla = check, look at
• se över = look over, review

So:

• Skulle ni kunna kontrollera tidtabellen... = correct, polite, slightly formal
• Kan ni kolla tidtabellen... = more casual

Yes, it sounds fairly polite and somewhat formal because of two things:

• Skulle ni kunna... is a polite request form
• ni can sound formal or service-oriented

So the whole sentence has the tone of something you might say in:

• customer service
• travel contexts
• formal writing
• polite public interaction

A more casual version might be:

• Kan du kolla tidtabellen innan vi åker?

That is much more everyday and informal.