what is the problem with my radio ?

hi- i drive a 2001 audi A4 1.8 T (quattro) i have had some problems with this radio for over 5 months. everytime i turn the car on the radio doesnt respond. it doesnt turn on at all and hasnt ever sense i let one of my friends work on it. at night time the lights on the radio dont work and it basicallly is lifeless. how do i fix this problem. i need help.