Is is ok to use Select/Deselect All here or better to shorten it to only select all. Would the users know that if they uncheck the "select all" checkbox. Everything will be disselected
I think there are 2 possible confusions here:
What I would do is make it a button (or a link if there's a more important button nearby). The button label (or link) should only be the available action: "Select All" if not all items are selected, and "Deselect All" otherwise.
Edit: after showing this answer to a co-league, I want to point out that if there are a lot of check-boxes, it's worth having both buttons/links available (it can be exhausting to deselect dozens of check-boxes manually).