I tried your document (exported as epub) on my Kobo Clara HD. The formatting is causing problems.
On Kobo native reader it crashed a lot, specially while changing fonts so it was unusable.
On Koreader it worked better, the bilingual text appeared correct. Only the first page has been recognized though and I could not change font size.
Arabic support was never ideal for me on the native kobo reader, so I prefer Koreader for that.
Follow this guide here to get Koreader installed with only few steps:
https://www.mobileread.com/forums/sh...d.php?t=314220