The nominal adjective "uncircumcised" can be stated as an adjective. AT: "these people who are uncircumcised will come" or "these uncircumcised people will come" (See: [[rc://en/ta/man/translate/figs-nominaladj]])
Here "uncircumcised" represents people who do not belong to Yahweh. AT: "these people who do not belong to Yahweh" or "these heathen Philistines" (See: [[rc://en/ta/man/translate/figs-metonymy]])
Saul probably stuck the handle into the ground and leaned on the point so the sword would go through his body as he fell down. The action is a metonym for the result, death. AT: "killed himself with it" (See: [[rc://en/ta/man/translate/figs-metonymy]])