I think I see what is happening now, there are a couple different things going on at the same time.
Signal loss alarms:
You suddenly started getting signal loss alarms from the official LibreLink app after you removed the DiaBox app. This makes sense; when you had DiaBox installed, the bluetooth connection for LibreLink wasn't enabled because the sensor can only have a bluetooth connection with one app at the same time.
When you removed DiaBox, the LibreLink app took over, and started giving you signal loss alarms.
Very annoying, but usual behaviour for this app. Which is why so many people turn off the signal loss alarm.
Lost data:
When you uninstall the official LibreLink app and download it again, the data stored in the app will be lost because you removed the app. Those data are now forever gone from your phone.
LibreLink and LibreView:
LibreLink is the app on your phone.
LibreView is where your phone sends the data whenever you have an internet connection, in the cloud.
This is where your team gets your data from, they do not go directly into your phone or app to watch (which would be creepy!) but they log into this LibteView cloud.
On a PC/tablet you can log into LibreView as well, using the same log in details as for your phone app.
Your data will be stored there, and it has some extra graphs as well, compared to the phone app!
Just go here and follow their instructions:
https://www.libreview.com/