First of all, if you go back to the 300BC you will find yourself in the Seleucid empire which controlled the area at the time following the division of the Macedonian empire as expanded under by Alexander the Great.
If any officials approach you they will most probably be either the city guard or posted soldiers in the service of Seleucus.
Unless you've gone out of your way to look extraordinary by wearing blinky lights or the such there is no reason why these guards or soldiers would be afraid of you. They are serving in one of the most cosmopolitan areas of the time and are used to seeing people with exotic features or dress.
Depending on the mandate of the officials they might not feel inclined to deal with you unless you try to enter the city or if you are harassing people. They are keeping watch over an area that might or might not be under threat of revolt due to the presence of occupying forces. They are busy. They don't care unless you make them care.
The first thing that will annoy them about you when they do care is that you are unable to make account for who you are and what you are doing there. You might be showing them some amazing things, but you don't respond when they ask you if you intend to sell the objects in the marked and you don't seem to understand that you need to pay the tax to enter the city with merchandise. You might also be an entertainer, but your show is more confusing than compelling.
The officials are struggling to understand why you won't leave them alone. Maybe you need assistance with something, but after a while chances are that they will begin to wonder if you are a bit crazy. Maybe they will attempt to drive you off or give you a beating to make you leave them alone.
You would have had a lot better chance if you had bothered to learn a bit of one of the ancient languages spoken in the area of the time or if you had brought precious metals or gems to bribe the guards to let you into the city. Once in the city you might or might not be able to find men of science and show them enough mathematics to convince them that you were worth listening to. Then after learning and perfecting their spoken language you might after some years be able to explain the concept of moving through time. Upon which you might be deemed insane, or possibly divine depending on whether they actually believe you. Either way you would have to prepare yourself for your life being changed in unpredictable ways.
You would probably fare better in the past if you never try to explain that you're from the future at all.