@Perun even the quote you posted makes a clear distinction between Bulgars and Bulgarians. It might be an artificial/historiographical one (like Byzantines vs. Romans, f.e.), but there is a difference nonetheless – both a temporal differentiation and a difference of content. I.e. the Bulgarians are those people who emerged from the mix of the old Bulgars, Slavs and locals and who adopted the Slavic language and culture. The old Bulgars, on the other hand, (most probably) did not speak Slavic and even though some of them had cultural exchanges with the Antes and probably even included some Antean tribes during their migration to the Balkans, they were still not Slavic enough to be called Bulgarians. Hence why their cousins on the Volga, btw, are also correctly called Volga Bulgars and not Volga Bulgarians (although they also underwent radical cultural and linguistic changes throughout the ages).
As for the OP and its mistakes, here’s a post about the early Bulgar history I had written several years ago, which goes into a bit more detail on the matter (though things can be expanded even further, of course).
But to put it even shorter, here’s the abridged version: Once upon a time there were a group of people living between the Black and Caspian seas, who called themselves Bulgar. The Huns eventually came by and conquered them, with some of the Bulgars moving west with the Huns and mixing with them. Thus the Bulgars were split into two branches – Western (Kutrigurs) and Eastern (Utigurs). After Attila’s death and the ensuing chaos, these groups (along with various other tribes in the region) fought all over the place, including with each other, until they were eventually conquered by the Avars and Gokturks. Then came Khan Kubrat, who rebelled against the Avars and managed to free and unite both Bulgar groups, along with a few other tribes in the region (the Hunnic Sabirs, f.e. – the ancestors of the modern Chuvash), thus creating a state of his own, which the Byzantines later called palaia megali Boulgaria (Old Great Bulgaria).
But after Kubrat’s death, despite his legendary last will, his five sons split the country between themselves and were soon vanquished by the rising power of the Khazars. The oldest son Bat-Bayan became a Khazar vassal and his Black Bulgaria formed an important part of the khaganate. The second son Kotrag (probably named after the Kutrigurs, which he inherited) took his people up north, to the Volga and Kama rivers, where his successors later created the so-called Volga Bulgaria, initially also a vassal to the Khazars. The third son Asparuh took his people west, where he eventually conquered Moesia from the medieval Romans (aka Byzantines) and carved up a country of his own there. The fourth and fifth brothers (Kuber and Altsek) tried to stage a coup in the Avar khaganate, but failed, so they dispersed again – Kuber took his people to the Pelagonian fields in modern Macedonia and became subject of the Romans, while Altsek first moved to Bavaria and then to Italy, where he became subject of the Langobards. Of the four brothers, only Kotrag and Asparuh managed to form countries with a lasting legacy. Kotrag’s Volga Bulgars mixed with the local Finno-Ugrian populations (and eventually the other steppe peoples from the south), eventually converted to Islam and developed into a strong trading hub on the routes from north to south and east to west, until they were finally destroyed by the Mongols in the mid-13th century. Asparuh’s Danubian Bulgars, on the other hand, mixed with the Balkan Slavs and pre-Slavic populations (usually termed Thracians, though Byzantines would be technically more correct), eventually converted to (Orthodox) Christianity and adopted the Slavic language and writing, which they developed and propagated across Eastern Europe (under Roman/Byzantine example). In 1018 they were conquered by the Romans, but managed to secede and form their second empire in 1185, until they fell to the Ottoman Turks in 1396, from which they were liberated with Russian help in 1878.
So, basically, it becomes pretty obvious that the Danubian Bulgars are not in any way descended from the Volga Bulgars (and didn’t even arrive from that region either, but rather to the south of it), but they’re both two separate branches which split off from the Old Great Bulgaria, which existed for a short while on the territory of modern Ukraine and Southern Russia. The two states, Volga Bulgaria and Danubian Bulgaria, existed for several centuries “side by side” (though actually quite far from each other), in two separate regions, and had little to do with each other. We don’t know if they even knew of each other (though it’s not impossible, since there’s the mission of the Hungarian friar Julian in the early 13th c., who passed through both countries while searching for the Magyar homeland).
Thus, when you’re speaking about modern (Danubian) Bulgaria and claim that “once instead of Orthodox churches Bulgaria had Minarets”, you should probably explain that the only minarets in Bulgaria are the Turkish ones, which appeared many centuries after the Bulgarians had their Orthodox churches.