1, First solve out all the Laptop peripheral devices problem.
PC Control Panel, Device Manager. Is there any peripheral devices get yellow exclamation mark? Solve that out first.
Google: Malwarebytes, only use free version,download and install, click scan, delete any trojan find.
2, And check the laptop model, does it compatible use Windows 10?
3, Come back here and show you what to do then.
4, For your 90 years father, it is more easy to use Windows 8.1 than Window 10.
The above picture, show the different between Windows 8 and Windows 8.1. Windows 8.1 just get back some old feature missing in Windows 8. It will more easy for your father get use to it.