Even with the limited vocabulary (which I think is a decent idea), there’s still a fair amount of strangeness. For example, at one point it says 怪物は力がある, but the idiomatic word here would probably be 持つ (which is already in the vocab list).
Another thing that stuck out to me was when the guy got stuck in a tree and they said 木の中に – a quick google image search confirmed my suspicion that this would probably be taken to mean literally inside the tree, like…embedded in the trunk or inside a hollow area.
Pointing to animal tracks on the ground and using あれ is weird – that should definitely be これ. It’s weird to see these adventurous guys call themselves 私 and using て-form to make requests instead of using imperative form, especially when everything else is pretty casual. Shouting 怪物！ at the monster seems like a very English-first pattern…if it was 怪物め or 怪物よ then that would be a lot more acceptable.
It’s certainly not the worst thing I’ve ever seen but I wouldn’t recommend this to anyone personally.