Learn Swedish: Ska vi asfaltera den där gångbanan till julen? - Are we going to pave that walkway by Christmas?

This is the standard way to refer to a specific upcoming holiday in Swedish. By combining till with the definite form julen, it specifically means 'by this coming Christmas'. While till jul (indefinite) is also heard in casual speech, the definite form strongly points to the specific future event.

Does till julen mean the paving will happen during Christmas?

No, in this context till means 'by' or 'in time for'. The sentence asks if the walkway will be paved and finished before the holiday arrives, not that the work will take place on Christmas day.

Why do we need the -n at the end of gångbanan if den där already means 'that'?

This is a classic example of Swedish double definiteness. When using the demonstrative den där (that), the noun that follows must also take the definite suffix. So it literally translates to 'that the walkway'. If you said den där gångbana, it would sound grammatically incorrect to a native speaker.

Can asfaltera be used for any type of paving?

No, asfaltera specifically means to pave with asphalt or tarmac. It comes directly from the word asfalt. If you were paving the walkway with cobblestones, paving stones, or bricks, you would use a verb like stenlägga or lägga plattor instead.