Hi,
I’m using a Samsung Galaxy A5 2017 (a5y17lte) as well and I had the same problem with the original camera app.
It is in fact a known issue, and a gitlab issue had been created a while ago but hasn’t been fixed yet : All pictures (JPEG) taken with Open Camera are 30.4MB (#1273) · Issues · e / Backlog · GitLab
So a possible workaround is simply to use another camera app.
Personally, I use Simple Camera from F-Droid which works fine.
You can also uninstall the default Camera app using this method if you don’t want to keep both : Uninstall default apps - #29 by AnotherElk
Hope this helps !