Well, as I said I can't really help from an X5 perspective but I do quite a bit of this sort of thing in my bands so perhaps if I give you an idea of a general approach you might take, and with a bit of luck it's quite possible someone who has some X5 experience or has even covered this song might be able to chime in over the top later on with some more specific advice.
I find the best way is to try and locate sounds on your keyboard that are quite close to what you want to achieve, then it's a case of getting your hands dirty playing with the different synth parameters on your keyboard to learn how each change impacts the sound. I had a quick look at the Owner Manual and although this 'board doesn't have the deepest synthesis engine going around, I reckon you'll be able to get pretty close to what you're hearing with a bit of trial and error, assuming you have a good number of present programs to begin with as raw material. A good tip is to save your work as you go, as you might progress to your final sound little by little without really "nailing it" on the first attempt to create it.
I'd start by trying to find a sound on your keyboard that's close to the synth pad you can hear in the background. You'll have something similar on there already that you can either simply run with or modify slightly.
The bright chord that only sounds quietly in the first beat of every bar sounds like a guitar run through a few effects to me.
The high-pitched percussive notes - you might start with some marimba or koto-type sounds and see if they're close to begin with. Or you might have some quirky sounding synth leads you can use as a starting point.
Then it's a matter of doing some sort of a keyboard split, I'd probably look to layer the pad and guitar sound (unless you have a guitarist doing it) over the top of each other on the left and the higher pitched sounds on the right. On Korg keyboards this is done via "Combi" mode.
Hope that's part-way useful. To be truthful editing and creating sounds on a synth is very much a trial and error process. The more you mess around, the more you learn. Good luck!
FWIW...not the most exciting song you picked there...C,D,C,D,C,D...yawn.....
