There you go, use that screw to set the tripping point.

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Looks like turn the screw in to tweak it towards the open position. Push the screw (the bimetal strip) and see if this indeed opens the contact

Turn the screw somewhat in that direction

Try to push the screw again to see how the contact opens, and when you release then how it closes. If it does not close back when you release, or if it is allmost in this condition, then you turned it too much, go back

You can also try those electronic photocells with a silicon sensor, I think they are better made and have a longer life.
But they might be harder to find, and more expensive.