Can't login into iCloud on iPhone 6 with iOS 12.5.7

I managed to go through configuration with Recovery Mode and I logged into iTunes through App Store, but when I want to log into iCloud to sync my data it keeps telling me to update my software.

iOS 12.5.7 is the latest version for this model. I tried to update it through my MacBook but it just stops after 10 minutes and disconnects my phone.

I also changed my Apple ID password and updated my MacBook to the latest version available.

Please don't redirect me to any articles - I've read all of them.