when taking off, what direction do airlines go on a runway?
like lets say the (13R/31L) runway if they take 13R do they taxi to that end of the runway? or the other end (31L)
I wanna film a takeoff (with the airport in background) when me and my dad go visit germany, in two months

 

The runway number is basically the magnetic heading you would see on a compass while taking off. 13R is 130 degrees, the R is used for the Right runway when there are two or more parallel runways at an airport. JFK has 4 actual physical runways, making up 8 runway designations, the 4/22s and the 13/31s. When directed to takeoff on 13R, a plane will taxi out to the beginning of that runway so as to be going in the runway direction on takeoff (and landing as well).

At JFK, 13R is on the west side of the terminal buildings, starting from the northwest corner of the field, aiming southeast. Do a search for airport diagrams to see the runway layout for a particular airport.

Which runway is in use at a particular time is mostly a function of which way the wind is blowing and how the traffic in an area is being handled, plus noise constraints. JFK late at night uses the 31 L&R combination unless the winds are too strong. Just about every airliner has a 10 knot maximum tailwind limit for takeoff and landing. The crosswind limit is a function of individual airplane design, generally in the 30 to 40 knot range.

Hope this helps you, enjoy your flight!