Back on topic, I think I need another info.
Arena page lists HP penalty for 1, 2, 3, 4, 5 and 6 days. I've noticed that some deck are in top 500 longer - like some deck in bronze is 10 days old at the moment. Do I assume right that HP penalties for next days, 7-10 are like -128, -256, -512, -1024? If yes, that's pretty funny that this 10 day old deck is still "visible" because it should have 0 HP? or probably 1 HP. On the other hand I noticed that this deck is only losing now so that could be true BUT it is still in top 25. I wonder why.
Another question, I wonder how game calculated my current deck level when I returned to play after two years. My first thought was my personal win-lose ratio I got so far. But I noticed that when I am winning by farming bronze (=improving my personal win-lose ratio) my arena deck level is going down so it can't be it. If no then how?