Fiat Punto Selecta Automatic

Hello forum, I have the following problem: With my Punto Selecta (Bj. 1996) the gearbox cannot be switched cleanly from N to D or R – from P to R and back it is no problem. The “turn from N to D or R” only goes with great effort and sometimes I get a noise, as if you were trying to take a gear without the clutch. Further the engine dies when stopping sometimes. …and to bad last the automatic belt squeaks The transmission oil is clean, no chips on the oil tank magnet, the transmission oil filter only pollutes minimally, the transmission oil level is correct, the disc wheels in which the thruster belt runs are without any grooves, all parts in the control cover are clean and common. I suspect the magnetic powder coupling, but have zero documents for the transmission and find no documents for the transmission. More problem: The Fiat dealers in the mei ner area have no idea about the automatic transmission and always want to turn on an exchange gearbox quickly–>unfortunately exceed the prices (as well as a chapter for itself, the clutch should cost e.g. approx. 1100.- Euro!) then almost the time value of the Punto ́s. Can anyone help me??? Thank you.