apps won't open

i'm working on a late 2011 macbookpro, with os x 10.9.5. some apps don't seem to open: mail, preview, calendars, appstore, terminal and more. i have no idea what could have caused it, except a program like "clean my mac", that i used in order to get get rid of some unwanted files, and i'm afraid it caused the damage. did someone ever encounter such problem? thank you