Extra - yet another word that comes from Latin and is used in Slovak and in English, but with different meanings. As usual, the Slovak sense is closer to the original Latin, while English usage has developed and distorted its meaning. The Latin meaning was "outside" or "apart", which is preserved in the English "extraordinary" (out of the ordinary), and that's the idea I get from the Slovak usage, like "Bolo to niečo extra", which I might translate as extraordinary, or maybe as "really special".

So the ice-hockey league which HC Košice play in is the "special league". The English sense of "extra" is like "naviac" or "navyše" in Slovak, so you could have an extra portion of fries (more of the same kind), or get something for no extra charge (no increase in the price). Many hotels here offer an extra bed in the rooms - it's nothing special, but it's in addition to the other two. Don't say that a film or concert or meal was "really extra"; say that it was "really special".