Mini Cooper R50 116PS oil pressure oil lamp lights up

Hello Mini Friends I have a Mini Cooper R50 2002bj 0005 719 key number 116PS I have a problem that is well known with the Mini and read a lot on the Internet but really nobody had a solution for the problem. I hope you can help me. I bought the Mini and oil lamp was already on idle. I made myself smart and many said I should make an oil change and reset filters. So oil change had even bought the good oil. 5W-30 Edge v on Castrol Original oil filter bought by BMW. and no Oil lamp still glows at the stand gas. At 2000 revolutions it goes off. If I press up to 6000 turns once correctly on gas then the oil lamp stays at 1000 turns off if I take gas away for several seconds. today I also changed the oil pressure switch. The problem still exists. I don’t know where it could be. Hope you can help me