Help required to recover admin account got access restriction

After mounting a new version of PostGreSQL I did also the following updates. I couldn’t open any if theinstalled apps. So I shutdown the systems and started again but still I cannot open system preferences! How to change the admin to default whih was there before I installed the PostGreSQL? Can I recover the documents folder and other user account folders while still having PostGreSQL installed? The root folders are visible in command prompt but have restricted access. Kindly help me to correct my system.