No Gears While Engine Running

Very strange problem, started Audi 1.9Tdi Avant this morning and it made a funny noise and the engine overrun for a few seconds and then sounded ok, So I carried on with my journey then heard a few funny clattering sounds a whizzing sounds with rattles but car just drove as normal, I got back home and looked under the hood to see what’s going on, first thing I looked for was belt problems and found nothing, went to start car again and just got a clunk from It, tried it again and it started but there was a rattle from somewhere under the engine, after a while it disappeared, I revved the engine up and all sounded ok so I left it. The next day I got in and started no problem until I tried to put it in gear, nothing no gears 1-2-3-4-5 and reverse nothing, turned engine off got all gears.

So I decided to put it in first and start it with clutch out ( of by the way the clutch feels fine) it started with a lurch and I pulled it out of gear instantly I found it had all gears while engine was running, so I drove to town about 6 miles changing gears all the way fine, Parked went to shop, got in and started it NO GEARS AGIAN WHILE ENGINE RUNNING, So I started it again while in gear and all was ok again, so now im worried to drive it. Has anyone any ideas, do you think its fluid top up or change ?? thanks guy’s in advance. Sam.