Ok the person who sold it to you just didn't want to do all the work or simply didn't know how -doesn't
sound like they would even know how to spy on you, lol
What you need to do is erase your hard drive and reinstall the OS
to do this the easy way you need to:
#1 go to apple store and download the latest OS version of OS available free of charge to you
#2 google "disc creator" download it free
#3 insert 8gb flash drive in to your comp
$ 4 Lunch "disc creator" and follow the instructions (pretty ease if you can read English) -this creates a fresh OS installer you will need to apply to your system after you erase the computer
#5 restart your computer holding CMND + R -dont release until you see a window with four options
one of which will say "disk utility" select that option then find "Macintosh HD". Under it you will c a subfolder with partition name which you need to select to ERASE (do not erase Macintosh HD) under format options select
Mac OS Extended (Journaled)....click erase
#6 insert your USB drive and restart the computer holding down "option" key, don't let go until you see 2 drive options one of which will be USB u created -select it and it will install the new OS. which can take up to 30 min....faster on newer Macs....Next time your computer restarts it will be BRAND NEW
Good luck!
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PS: If for some reason after you select the drive it will give you 4 options instead of installing right away, select the option that says Install Mac OS X (or something similar -may not b exact wording, but you will recognize it from obvious choices) again and it will run the installer.