In many dialects of Arabic, أهلا (and مرحبًا) would translate to "welcome," and not "hello." For "hello," you can use the Muslim greeting "As-salaamu 3alaikum" ("Peace be upon you"), or if you're going for something less denominational, simply say sabaa7 ul-5air or masaa2 ul-5air ("Good morning," and "Good afternoon/evening," respectively.)
explains the use of those numbers https://www.iwillteachyoualanguage.com/blog/arabic-chat-alphabet
From my experience, in Jordan people use Marhaban (مرحبًا) when you start speaking to someone as "hoi, hello, hi there....) and Ahlan (أهلا) is said to you when you enter some place as "welcome" - sometimes like entering a shop you say Marhaban to the sailsman and he answer you with Ahlan... (ofcourse they say those terms in their dialect which sounds a little different from the MSA, but you get used to it quickly)
Is there a reason why the letter ''noon'' is not being used at the end?