Your issues with Play store, reminds me of 2 x similar incidents, i had with my old Note devices.
Think it was Note 3 and my Note 4. Not sure.
Unfortunately It was a few years back!
eg.
When i tried to download, an apps update etc and
app size was eg 2mb or 5 mb.. etc I struggled to download.Very frustrating!
Eventually after a week or 2, maybe 3.
i was able to pinpoint
the the "suspect"
(Unfortunately i cannot remember clearly ,
but it was either, that i had sideloaded
wrong updated version of Play services apk
(Cleaning Play services cache did not help.)
or it was an Xposed /Xposed model.
(So phone was also rooted)
Anyway ,
i then decided to factory reset and Playstore
was working fine again.
Bottom line is
you can either look for the "suspect"?
causing this.
( I know there was a few threads about similar issues with Playstore, on XDA... way back then ! )
or save yourself from the frustration it's causing?
and try a "clean" Factory reset.!
Good luck