Defected gearbox, failure of cruise control

Servus dear community. Was before a week with the fat on vacation in Italy. The first problem, the cruise control didn't work and that almost exclusively for highways. Man. If I'm not mistaken, then when the cruise control is activated, a sign appears in the AI. This has certainly not lit up. In addition, I made a noise from half on the way back, which became louder and louder in the course of the Km. First I thought of a wheel bearing. But at home on the stage, the sound came out of the gearbox. It's a six-speed switch. I then checked the oil and then filled up a whole litre. Who knows about gears and can give me a tip about what to do? Thank you.