Traveling Merchant in the Apocalypse

One day a floating screen suddenly showed up for me. What? Traveling merchant? Trading? Farming? Armor? What do you mean by the fall of humanity? Can’t you stick with one genre? I just wanted to graduate!
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Hi, I'm new here, you can find me here or at RoyalRoad. I will try to update at least one chapter every week.
English isn't my native language, so let me know if there's anything that seems strange when I write it in English, so I can try to adapt.
For now, I'm not sure about everything in this story, just there is a system (I tagged it, but I'm unsure if I can say it's system leveling?), a female protagonist and there will be an apocalypse.
It's apocalypse, so it will probably have some sensitive content later, even if not much, so beware.