Hello, and Welcome to the HP Support Community!
Your ChromeBook does not have a "hard drive" - it has a memory chip used for storage. It's soldered to the main board.
(I'd be careful going back to that computer repair shop!!)
Check out this webpage for some suggestions to speed things up:
https://www.computerworld.com/article/3333005/chromebook-tune-up.html
WyreNut
-------------------------------------------------
Former Expert in the PalmOS, WebOS, and Android sections of this Community Forum.
I am a Volunteer here, not employed by HP.