Short answers, pulled from the story.
The First Bulgarian Empire was founded in 680-681, when the Bulgar leader Asparuh defeated the Byzantine army led by Constantine IV and forced the Byzantines to sign a peace treaty recognising Bulgaria as an independent state and obligating the Empire to pay annual tribute.
Asparuh was the third son of Khan Kubrat, the ruler of Old Great Bulgaria. After Kubrat died between 650 and 665, the Khazars dismembered the confederation, and each of Kubrat's five sons led his followers in a different direction. Asparuh moved west to the lower Danube, eventually crossing into Scythia Minor and establishing the Bulgarian state in the northeastern Balkans.
Bulgaria converted to Christianity in 864, when Boris I accepted baptism, taking the name of his godfather the Byzantine Emperor Michael III. The Bulgarian Church was formally recognised as autocephalous at the Fourth Council of Constantinople in 870, and the fully independent Bulgarian Patriarchate was officially recognised in 927.
The Early Cyrillic alphabet was invented in the Bulgarian capital Preslav during the reign of Simeon I, building on the earlier Glagolitic script associated with the disciples of Cyril and Methodius. Bulgaria's adoption of Old Church Slavonic as the official language of the liturgy in 893 and the subsequent production of literature in these scripts caused Old Church Slavonic to spread north and become the lingua franca of much of Eastern Europe.
The First Bulgarian Empire fell to the Byzantine Emperor Basil II, known as "the Bulgar Slayer," following decades of war. After the decisive Bulgarian defeat at the Battle of Kleidion in 1014, resistance continued until 1018, when the last Bulgarian strongholds surrendered after the death of Ivan Vladislav during the siege of Dyrrhachium. The empire was succeeded by the Second Bulgarian Empire in 1185, when the brothers Asen and Peter liberated the country.
After the Battle of Kleidion in 1014, Basil II ordered 99 out of every 100 of the approximately 14,000-15,000 captured Bulgarian soldiers to be blinded, with every hundredth man left with one eye to guide the rest home. When the blinded army returned to the Bulgarian Emperor Samuel at his residence in Prespa, Samuel suffered a heart attack at the sight and died two days later, on the 6th of October.