SupaDupaFresh
Superstar
So this song is in the key of B major.

Here is the B major scale. These are the ONLY notes you need to play around with and worry about, whether you're looking for chords or finding a melody/bass line. Forget all other notes on the keyboard.
But I'm gonna take it a step further:

This is the B major pentatonic scale. Now it's been broken down to just 5 notes (penta meaning five): 4 black keys in consecutive order, just one white key, B. Pentatonic scales are SUPER important to all black music, the blues, and pop music melodies.
You can remember this scale without even taking advantage of your DAWs features, easy. But chances are your DAW has a "chord mode" or "scale mode" or something that allows you to set a key and scale so you can see it from there.
Here what I want you to do: play around with the pentatonic scale along with the song. Dont play any chords yet (your sample fulfills your rhythmic section anyway). You can try improvising a bass line or you can try improvising a lead melody. But play along with the song using JUST THESE FIVE KEYS.
Come back and tell me what you think.