Operating system not found in Windows 10

This is a screenshot of Acer V5 after the system restart after Windows 10 updates. The message shows "Operating system not found".

Current notebooks have two boot options which are legacy and EUFI compared to old models which uses BIOS only.

How to fix it:

1. Upon power on, press ESC key to enter BIOS.
(Other model uses different key such as F2 or DEL or F1)

2. Go to boot option and on boot