Why does Minecraft think it's offline?

Quick Solution

This might not fix it, but if anyone has this issue make sure you are allowing Java Area Runtime through the Windows Firewall.

Stop Minecraft

If Minecraft is still running and you cannot stop it by normal means, go to CMD, and enter this:

taskkill /im javaw.exe /f /t

This ends Java Area Runtime. Sometimes tasks won't stop themselves when asked, so we do it forcefully with /f. The /t is to end processes started by it, which would be Minecraft.

How You're Getting Rid of It

You said you were "deleting" it. While this might be a simple terminology mistake, if you are deleting files do NOT do that. You should be going to your apps and having Minecraft uninstall itself.