I have googled around for hours how to fix it but nothing seems to work.
I would appreciate if someone could help me! 
Hello i found a topic which help me with the same problem. Here is a link 
Hotfix for Agent not installing
You better just wait for the fix or at least reply from Blizzard. Not gonna solve your problem tho cuz you’ll just stuck at battle.net agent update after 
Hey everyone,
We appreciate you all taking the time to report this. Our teams are investigating the issue, and we will be providing updates on our active forum thread located here: