How can I detect in activity log if 'PC repair shop' guy had a look at my files I’ve got sensitive data on my Mac.

I’ve taken it to a repair shop, because my mac was not able to boot. They are keeping it till 28. December.
I gave them my password.

I’m scared they will check and see some of my folders/text files.

So, is there any way to check activity/system log? I would like to see when and what was opened/viewed.
In short, if they really, really wanted to look at your data, they could do it in ways that you could not detect.

What generally happens, though, is that these professionals - whose job relies on their reputation &amp; integrity - simply couldn't be bothered even checking to see if you had anything more interesting than a couple of dodgy torrents.