I don't know why someone should tell you to try the updates in Safe Mode as updates don't work in that mode.
Can you check that the date and time is correct as that would stop any updates just as a 3rd party antivirus program can and it's worth disabling yours to see if the updates succeed, but it's unlikely that the default Windows Defender would cause any problems.
Go Start - Settings - Update & Security then click on Activation to see what that says - it will tell you your version and if it is activated.
You can download the ISO from
https://www.microsoft.com/en-gb/software-download/windows10 by clicking on the Download tool now button and read the section for Using the tool to create installation media.
This will auto download the version for your system and includes the Anniversary Update to take you initially to 14393.0
From within Windows, open Windows Explorer/This PC - insert the disk then double click on the DVD drive to run the setup.exe.
You should be able to update with that, but first disable any 3rd party antivirus program, go into Task Manager/Startup and disable all items then go Start - type msconfig and press enter.
Under the Services tab check the box to Hide all Microsoft services - Disable all - Apply - OK and restart, but it's a must that you check the box to Hide all MS services before you hit those buttons.