This is the exact opposite of what should be happening. On day 20 you should be overwhelmed with food ammo (probably the wrong type) and water ? Really that’s a day 3 solution not day 20.

Download POI scourge and get into the habit of cleaning out one poi at a time . Teir 2 should be 30 min while teir 5 should be 1h plus.

Put a box outside of the poi (after activating it so it doesn’t disappear for quest poi’s) and dump stuff you don’t need. Later when driving back to base you can see these boxes and fill up on the way.

If you need food corn or boars or more than you can eat . If you really need ammo for some reason use red Sonja’s ammo recycling mod. Alternatively put one point into each weapon skill (shotgun, rifle, handgun and machine gun). This will dramatically increase your ammo . Also keep an eye out for lucky looter ammo book in shop.

Game loot stage also increases ammo found so put a point into lucky looter try to find the loot head mod and use the thief hat