It has plenty of meanings and can be used in different sentences and still sound right to the Tagalog ear. The different meanings and different contexts wherein it is used are too many and I cannot exhaust them all either here or in other platforms. It is an amazing, baffling word. Trying to study and speculate on what could its etymology be, or what are its main root words...we can see "na-" is "already" and "-man" is "ever". So we can say it is, "already-ever". Substituting 'now' for 'already', we can say naman is literally, "now-ever". IN its core meaning may lie something about time and space. Like, "so far", "in all the world", "eternity". Mabuti naman is, Good, so far. Ayan ka na naman is, Here you go again, implying, "In all eternity and in all the world", you have not changed and you do the same things again and again. Ang ganda naman is, How beautiful really!, implying, "So far", "in all those times" I've seen you , you are exceptionally beautiful today! ANg pangit naman is, O how ugly and there seems to be hopelessly nothing "in all the world" that can be done about it. Ikaw naman is, Now, it's your turn, your chance, your "time". It can mean anyway, (Kahit na, maganda naman eh!)or contrariwise, (Maganda nga suplada naman.) or on the other hand (Sa kabilang dako, gumagawa naman siiya ng tama). It can mean intense emotion or mediocre emotion. As in, ganda naman (intense) and okay lang naman (mediocre). It can be a plea, Wag naman po! Please!No please , not ever in all the world! A rebuke, Naman eh! Naman naman! But most often it means again, paired with na...Eto na naman siya. In all eternity, in all ever, nothing has changed in what he is doing everyday. SO, it could mean a lot of things and still sound right. I think it implies time and space, changes and non-changes in the "ever there" cycles, times' and events of life . Poaitive or negative, welcomed or rejected, alarming or calming.

It can also mean AGAIN like in the question, "Umuulan na NAMAN?" which means "Is it raining AGAIN?"

I cant answer you literally because it cannot be explained by details.. but somehow naman is used to mean "other" We often omit it when we translate things in English.. Such as : Wala naman yung bata dito.. : The child(bata) is not here (wala dito). Did you get it ?

it depends on its sentence

it means an expression of gentle protest or denial or "also; too; rather; again; on the other hand"..