The phrase "upon you" means that they are ready to capture him. AT: "The Philistines are here to capture you" (See: [[rc://en/ta/man/translate/figs-idiom]])
It is implied that if Yahweh left Samson, he would no longer be strong. AT: "But he did not know that Yahweh had left him and that he would not be strong enough to defeat the Philistines" (See: [[rc://en/ta/man/translate/figs-explicit]])
# put out his eyes
This means that they removed his eyes from his head. AT: "removed his eyes" (See: [[rc://en/ta/man/translate/figs-idiom]])
This is a very large, heavy, circular stone. Normally, a large animal pulls the millstone around in a circle to crush grain. Here the Philistines humiliate Samson by making him pull it.