It really helps to listen to the original (or a cover version you like) several times, until the rhythm and flow of it become second nature, and it becomes almost impossible to play it wrong!
If I can make a suggestion, if you are working with a music teacher, ask them to suggest a regimen of ear training exercises. Timing and interval recognition and repetition are the foundation of playing well. There is a lot you can do to improve your playing, that doesn't involve playing at all!
And, if you aren't working with a teacher at all, at this stage, with so many possibilities stretching before you, now might be a good time to find one again. Look perhaps for someone that teaches, but also plays popular music professionally (or semi-pro) so they understand your needs...
Keep it up!
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An arranger is just a tool. What matters is what you build with it..!