@Adrian091: I can see that your screen seems to be takign up an abnormal amount of battery, therefore I recommend going to Settings > Display > Brightness (Reduce to a suitable level) > Auto Brightness (Off). It is also wroth trying the following energy saving tips to see if this helps.
- Enable Power Saving mode (Settings > Device Care > Battery > Power Mode)
- Switch off GPS, WiFi and Mobile data when not in use
- Disable or shut down any applications when not in use.
- Delete any recently installed 3rd party applications