So, give yourself some time to configure NoRoot Firewall in Android. And this is where Firewall apps come into the picture. If you are looking for a simple yet powerful app that requires no-root then you should try LostNet NoRoot Firewall. It will restrict the app from using Internet data until the app will run as a background service. You can follow above steps. Now, no apps will be able to use the Internet while they are running in the background. We are talking about Android here, there is an app for everything. The appeal of Mobiwol is that it is very easy to use and there are no complicated settings to deal with. Also, the app can be overwhelming for new or beginner users due to all the options and filters. On Android Smartphone, every app running in the background always use Internet data without your permission.
That way you could e.g.
How to Block an App from accessing the Internet Android Oreo
revoke the permission to access mobile data and/or WiFi just from that app: Your network connection would not be. Block an App from accessing the Internet on Android Oreo, Nougat, Once you come in the Network & Internet tap on the “Data usage” option. While you can block internet access on certain apps from Android settings, you can either block entire network traffic or on a per-app basis.
Scroll down the page and tap on the app which you want to block from accessing the Internet.
With just a single tap, you can either block entire network traffic or on a per-app basis.
Video: App network blocker android How to BLOCK WiFi devices with my Phone? [No Root] [iOS/Android] [Works 100%]
While you are using the app, it logs all the traffic. NetStop Firewall is designed for such cases. You can follow above steps.

He especially loves using Windows and writing about it.
NetGuard provides simple and advanced ways to block access to the internet - no root required. Applications and addresses can individually be allowed or. Firewall WITHOUT ROOT. Host name/domain name filtering, simple interface, fine-grained access control and no suspicious permissions on the firewall app.
While you are using the app, it logs all the traffic.

NetGaurd is very similar to NoRoot Firewall in that you can block individual apps from access the internet via mobile data or WiFi. As soon as you unlock your device, apps can connect to the internet.
Video: App network blocker android How to Turn off DATA For Any App in Redmi - Block Internet Access for Apps
Scroll down the page and tap on the app which you want to block from accessing the Internet. You can either block the app from connecting to the internet or allow it.
Not every one of us is looking to micromanage all the apps from connecting to the internet. In Android, you can easily toggle between mobile data and WiFi or even turn it off entirely as and when needed.
Just install the app, turn on the firewall and you are good to go. It is most useful for me because I want to use this data only for surfing.