Cemoniz, welcome to the community, and thank you for sharing your concerns about your device. What I would suggest first is clearing your cache from your Messages application. If this is still not working, try these steps:
Boot into recovery
- Press and hold Power, Choose "Restart" option
- When screen turns off, press and hold Volume Down and Power
- When the white HBOOT screen appears, use the volume button to move down to “RECOVERY.”
- Press the Power button to select “RECOVERY.”
- When the triangle and exclamation appears, hold the Volume Up and Power button at the same time.
- Using the volume button, scroll down to “Wipe cache partition” and select it.
- Select "Reboot system now"
If you are still unable to access your messages, you will need to complete a factory reset. This will wipe all data from the device that is not on your SD card and reset to factory default settings.