The Hints and tips menu gives you some tips on certain events and entities where it might not be super obvious what to do (use keywords to search for through the spoiler-marked ones), but the game otherwise just leaves you to discover everything by yourself.
If the game does give you hints/tips about certain entities, it should absolutely be through in-game notes left by previous workers. TR_1 has notes that have already done this; they hint at the appearance of a certain entity to help you identify it, then give you a hint for the crafting recipe of something that should help you deal with it.
I actually never knew about this letter, is it placed on an obvious place or under the rubbish or something? Also, i am quite aware of some entities, mainly the already existing ones from 6.3 to 7.x i believe. Yet, the game seems to have so many new things and i do have quite some trouble getting to certain areas, not knowing how to explore properly.
