Data usage is calculated In a time frame, that's why it will show a date like June 3 - July 4. The data usage it is showing you is what has happened from the beginning date to the current day. It's not still using data, it's showing data that was already used while you were using the apps mentioned. No need to worry. If your phone is slowing down then do some googling about how to optimize and speed your phone. Don't let your storage get close to being full. Comb through your whole phone, apps, settings, permissions, everything. The less your phone is trying to do at once the better, especially if you have somewhat limited RAM. Removing or lowering animations makes a huge difference to how speedy and responsive your phone feels. Restrict background battery usage to unused apps as well as background data. Turn off things like "ok Google" in Google assistant unless you really want that feature. But with it on your phone is constantly listening and waiting for you to say ok Google and that uses resources that contribute to slowing your phone down. Turn of Bluetooth and wifi when not using. Turn off nearby share, printer services, NFC. Think of things like that. Google will help a lot. Phones nowadays do so much by themselves, you just need to figure out whats happening in your phone and what's actually needed and what's not. DO NOT USE RAM CLEARING APPS as they can actually cause your phone to work harder and slow it down.