How do I fix my MacBook Air showing error 'cannot sync iCloud must delete iCloud data to log in'?

Hello all, I have noticed numerous settings getting changed on my MacBook Air when I log out and then log back in and the last fiasco my MacBook Air could not log me in due to a message stating “ cannot sync iCloud must delete iCloud data to log in “ and after numerous attempts I deleted the data and it erased all of my photos. After that I looked and my photo settings were on shared and my files were open that I had closed the night before

does this sound like a remote access Trojan ? Because I am at my wits end with this MacBook Air and then iCloud settings getting changed without my approval