Open task manager, end the Shellexperiencehost.ext process. That will likely correct it at least for a bit.
I was having issues with that occasionally (also upgraded from win7), along with other things like action center etc. An update recently seemed to have greatly reduced that issue for me.
For Cortana, make sure your indexes aren't screwy. Mine were. It was my fault as I had messed with library folder locations a few times in my Win7 install and some of that old stuff was still in there. Cortana wasn't happy with that. Once I cleaned up my index folders and had it reindex everything that corrected a lot of weird sluggishness with searches.