Well, im trying to make object(armor) which if you put on, you can get, for example model of compass in First-Person. Tried to make it in many ways, but all of them don't work. Is it possible to make this thing?

When the player wears an armor, the metaproperty linked to the armor with ArmorEffects flavor will be applied to the player, from there you can use a custom script like NVCreateAndLink to affect the player or spawn an object, objects are attached to the player's view like the compass HUD if they have the CamAttach property, so you just need to spawn an object that has that property set.

Oh, thank you Thief, Im going to try right now

It's already a somewhat advanced problem for a beginner, but someone can easily make a demo for this case, I can't as I'm at work.