Why won't my phone hook up to certain hotspots that's saved

When I first got the phone I connected my moms hotspot rto it to west it up. Worked does 2 days now IT won't connect at all and the hotspot is saved as a network.

Also why is it so slow.. Half the time I can't make calls I'm not getting all of my messages can't go on the play store and I've updated my apps plenty of times and don't even get to use them... Why?... Please help