Help in getting my Gear box fixed Alfa Romeo 156
My name is Otega, I convinced my sister to get an alfa romeo because I have loved the car without knowing much about it. unfortunately, it had a faulty engine and gear box. We purchased a new (used engine and gear box using a local mechanic and it worked. after a few days, the gear box stopped selecting. it show a red flashy light on the dash board and buzzes. I am hoping I could get help on how to fix this problem. anyone to bail me out. I appreciate this.