How do I restore syncing Outlook calendar with iPhone?

Hello,
I have some issues with my iTunes. It works great with syncing media files, but I cannot sync calendar events from my Outlook 2013 because it just stuck for few minutes and nothing happens. I never tried to sync this data before so I don't know whether it was always like this or it happened recently.
I searched for some solution and found software called Akruto:
https://www.akruto.com/sync-iphone-with-outlook/
And it works, which means the problem isn't in my Outlook or iPhone. Is there any steps how I could make iTunes work again?