Hello! Tried upgrading OS from ElCapitan to Sierra, but Sierra did not want to work so I used Time Machine restore to revert back. I didn't erase hard drive, just hooked external hard drive to Mac and chose to retore using Time Machine backup. But now I notice that Mac is bit slower when activating apps. When starting up, it takes maybe 30 - 60 seconds longer to get Libreoffice and Firefox running. Is that normal? It doesn't really bother me by itself, but I got tiny worry that what if I weakened system, security or something like that?