Check engine stays on all the time .. car slips out of gear when I go down hill.

What is your question?

Idk if 783 that is right code it says gear shifting it shifts into gears good it's when I slow down .. I go down the road at 25 mph stop at red light and all my gears lights are blinking and it's stuck in nuetral until I shut off engine and start back up.. light stay on. The car is automatic turbo diesel with 246 thousand miles on it.. car was well taken care of though please help me No noises no leaks

What makes this problem better or worse?

It only did it when car wasn't all the way warmed up. Now it's regular.

How long has your 2005 Volkswagen Beetle had this problem?

2-3 weeks