If the instrumental case in Polish is used to designate the tool with which an action, or state of being, is being performed/is, how is it that the instrumental is also used to express time and locations, professions, nationality and relations, etc.
Also, why is it used with certain verbs (być, interesować się, zostać...), and certain prepositions (z, na, przed...)?
I'm essentially struggling to understand how, from this basic premise of "tool with which an action is performed", other usages such as the examples used above can also be included within this same case. I have found no complete grammatical guide on this case (or other cases for that matter) online, because most learning tools focus on usage and endings without explanations.
Any help?