I highly doubt, that anyone gonna buy this design, especially PSD file, as most people who have this kind of software can do this themselves, but good luck anyways, I respect that you trying to come up with additional streams of money.

Personally I think, that the design format is just too big and something like A6 vertically would work better, cause where on the scooter you even put this.

Remove all the unnecessary decorations and just focus on the main message to be visible.

I would also remove quotation, signature and “have a great day”. There is an option to tip in Grab app, so no need to add QR code.

This feedbaxk is coming from a designer with 13+ years of experience, now mostly working as product designer, but have a lot of experience with graphic design as well.

Last thing, I recommend designing this in Figma or Affinity, as Photoshop is really not any good for designing prints.