Oil pressure too low/EPC light
 

Hello Audi fans, please help me! I have an Audi A5 1.8 tfsi and I got a light on dashboard when i start the engine, saying "switch off engine oil pressure too low". It came on and beeped light for 3 times then stops. There is another error that appears when i accelerate the car over 4.000 rpm, the EPC light comes on with the message "Do not exceed 4000 rpm". I changed both sensors (blue&brown) 2 times, but no results ! What should i do ? Sorry for my english mistakes btw.