History is supposed to be objective, not a concoction of propaganda aimed at giving a country (FYROM) a national identity. It's saddening to see your kin getting brainwashed by a guy who was grasping at straws after the Yugoslavia split. Here's some actual history:
2000 - 146 BC: Peninsula of Greece is populated by a bunch of different states (city-states), each speaking Greek (the language first derived from Egyptian in the form of Linear A and B and later from Phoenician after the Mycenaean dark age of ~800 BC), each believing in the same Olympic gods, sharing the same culture and customs, each however competed and often warred with each other. Being allowed to participate in the Olympic games, a form of ceasefire during continuous warring, was a form of confirmation of Greek identity. Notable examples: Mycenaean, Minoan civilizations, Athens, Sparta, Thebes, Corinth, Macedonia.
146 BC - 324 AD: The Greek city states are at an all time low after centuries of constant war. The Roman Empire is at an all time high, conquering Greece relatively quickly. Greek city states become vassals of Rome, like pretty much the entirety of Europe, north Africa and middle east.
324 AD: Constantine, a Roman emperor, shifts power to the east, creating a new center of his empire in Constantinope, thus creating a "second Rome". The empire is inherently Roman with Latin being the lingua franca, but the relationship with the west is starting to deteriorate, creating a new empire separated from the west.
620 AD: Emperor Heraclius changes the official language to Greek, being the predominant language in the empire. The empire achieves multicultural status, with Greeks, Latins, Jews, Kurds, Armenians being the dominant ethnicities, each living in segregation. The religion switches from Greek polytheism to Christianity In the meantime, Slavics descend to the south and amass behind the northern border in the Balkan. A few of them settle in Macedonia and live together with the Greek-speaking settlers who have been there since the Bronze Age.
700 - 1200 AD: Arabs/Muslim attack the eastern lands while Slavics (under Bulgarian rulers) attack the northern. The Arabs are mostly repelled but the Bulgarians are starting to gain territory. Eventually they are driven back to their lands north of the border. Orthodoxy as well as literacy spreads to the north to the Slavic tribes and reaches modern Russia. Relationship with the west is becoming hostile, after the Schism of the 2 churches (Orthodox and Catholic) and massacre of the latins in Constantinople. The fourth Crusaders, which were supposed to reconquer the middle east, stop by Constantinople and sack it as a means of collecting debt. The empire is at an all time low and will never recover.
1200 - 1453 AD: The Ottomans start to raid the west, slowly but surely advancing to the heart of the empire. Constantinople is sieged from all sides and falls. A lot of people fled and settled to the west, most in Italy and the area around Thessaloniki.
1453 - 1900 AD: The Ottomans invade Europe from Constantinople and reach Vienna, where they are eventually repelled back. Slowly, the Balkan region gains independence from the Ottoman regime, which is losing power and territory each year. There is a population exchange between newly founded nations of the Balkan and neo-Ottoman Turkey.
1900-1920 AD: Balkan wars about the disputed territory of northern Greece which was reclaimed from the Ottomans, with Greece being the victors.
I hope you gained some knowledge, now peace be with you.