Conflicts with subdomain

You need to set a prefix for each site or a different database index ??

After setting either you should flush both caches fully.

Can youn give me any instructions of how to do it? Mu hosting provider says they do not provide redis related help as they are not familiar with it. So plz give me any guide that I can do it myself.

You can find the configuration options here: https://github.com/rhubarbgroup/redis-cache/wiki/Configuration-Options

And a bit of an explainer here from the Pro version: https://objectcache.pro/docs/shared-instances/

Thanks, it helped.