Can't change theme back

[AC Question]

Hello, i'm new to this site so i hope i posted this in the righr section. Also English is not my native language so sorry for my grammar and i hope you understand what i mean.

Yesterday i downloaded a few themes and applied them. I downloaded the DarkKnight theme and applied it. I didn't really liked it so i deleted it. But the theme was still applied. So after i deleted the theme i'm keep getting a pop up which says "Themes has stopped" everytime i go to the theme store or my themes. It keeps popping up for awhile. I tried changing to other themes but i then says that it "could not apply this theme". Also when i try to change back to the regular theme it says that this theme has already been applied. But it hasn't. And when that happens all my other themes that i downloaded are gone and the standard theme has this check symbol on it. Its like my phone thinks its using the regular theme. I tried downloaden other themes but i cant. It gets stuck by installing the other themes. I also turned off and on a frw times but that doesnt seem to work. So please can anyone help me this is so annoying. And i really dont want to use factory reset.

Sorry for my english i hope you can understand it.