iPhone shows error while verifying after update

Good day everyone,

recently i tried updating my iOS using a wifi and after the download of the update, the update refused to verify. it showed an error while verifying. I had to delete the update and try again and it was still the same issue. just now, I decided to use Itunes to update the ios and still the same error, but this error is error 4000. i did it on Itunes twice. Now I am frustrated, I don't know what to do.

Also, this is in regard to my Apple music, my songs keep un-downloading, if that is even a word. whenever I download a song, the next day it just stops playing or showing. All my songs are gone. this is the second time this thing is happening. and i have paid for the music already for the month.

[Re-Titled by Moderator]