I can't get my radeon rx 580 gaming x 4g to stay at 30 mh/s

[Elseba]

I've tried messing up with the bios and with the overclocking but I can't make it stay at 30. At the start it goes normally, but progressively reduces until 25 and now to 22. Normally I wouldn't mind that, since that just happens to one of the graphic cards, but my stepfather would beat the crap out of me (maybe not literally) if I don't find a solution, because he is losing so many money and so many energy. I seriously need help, either with the mh/s or with legal ways to refuse keep working for him with this and "owe 20% of the money" which I don't care about