To enter Safe Mode on your Dell Latitude 7280 when experiencing a black screen at startup, try repeatedly pressing the F8 key (or Shift+F8 on some systems) during the boot process, before the Windows logo appears, to access the Advanced Boot Options menu and select "Safe Mode"
If the laptop is stuck, try a hard reboot by holding down the power button for 10-15 seconds until it shuts off completely, then turn it back on. 
repeatedly Press F8 (or Shift+F8): As the laptop starts, repeatedly tap the F8 key (or Shift+F8) before the Windows logo appears. 
Look for the Menu: This should bring up the Advanced Boot Options menu. 
Select Safe Mode:
If Safe Mode fails, try a system restore from the Windows Recovery Environment. 

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Hi

Could you try an external screen, like a monitor or TV that has HDMI?

Is there any kind of recovery option or USB you could try?