Can people look into my pictures somehow even if my iPhone is locked?

I'm taking my iPhone to a repair place to have my shattered screen replaced with a new one. Also, the sensor thing is getting fixed as well. I will leave my iPhone locked, but I'm concerned that they will be able to somehow hack into it and check pictures or information. I like keeping everything private. Can simply putting a lock on my phone prevent that? I don't really trust people

They can do it but it depends what shop you are using. If it is an independent store then yes, they probably will but if it's Apple care or something like that, they are professional so they don't really tend to hack into the phone of customers. You can transfer all info that you'd like to keep private onto your computer and delete it from your iPhone and then put it back. Hope I helped.