UEFI boot manager missing problem in Acer Aspire V5 473pg

I installed windows 10. Normally, There has no problem. But in today, when I turn on my laptop, it shows some waring like this "boot manager is missing. Please insert recovery image or installation media and hit any key". After I search my problem in google. Some people said "change your boot mode to legacy". So, I changed boot mode to leagacy and windows starting.

After that I also repair windows OS from installation disc. But the problem is, everytime when I turn on my laptop, boot mode is always change automatically to 'UEFI'. So, I need to change it to 'Legacy' again and again. How can I fix this problem without reinstalling windows?