In the meantime, I recommend the following:
1. Remove any unnecessary packages through ADB (https://www.xda-developers.com/uninstall-carrier-oem-bloatwa...)
2. Use Shelter (https://f-droid.org/en/packages/net.typeblog.shelter/)
3. Use a VPN-Firewall such as NetGuard (https://f-droid.org/en/packages/eu.faircode.netguard/) or NoRoot Firewall (https://play.google.com/store/apps/details?id=app.greyshirts...).