iTunes library disorganised, slow performance

I have recently bought a Mac Mini, and am in the process of moving my iTunes library from my MacBook Pro. Since the update to 12.2, the spinning wheel keeps showing up when i am trying to update song info (either for single songs or whole albums). The general program is totally slow. When I have transferred my library to the new Mac (250gb worth), the artists on the left side are no longer in alphabetical order, and artwork that was previously there disappeared. The artwork for most of the albums showed up immediately in the last itetation of iTunes, however, since the update it's an absolute nightmare.

my question is, how do i get the artists in alphabetical order on the left side scroll bar?