4-Speed Automatic Transmission

Hello.

I'm having a problem with my automatic transmission.
Car: Passat with AFN engine.
It shifts very abruptly from 1st gear in the 2-speed mode, and the harder the shift, the slower I accelerate (with little throttle). However, when driving at higher speeds (with more throttle), the shifting process is still acceptable.
The remaining gears shift smoothly.
My question is, what could this be? (I know that a remote diagnosis is always difficult, but maybe someone has an idea).

Besides that, I wanted to check the AFT (Advanced Flight Technology), but there's no way to measure it. How do I do that?
What needs to be done when you want to replace the AFT (Automatic Fuel Transducer)? Is there another filter or strainer that needs to be replaced or cleaned?

How can the motor control unit (ECU) be reprogrammed from automatic to manual transmission and back?

Thank you for any response.
And greetings to everyone.

Voss.

Hello.


Besides that, I wanted to check the AFT (Advanced Flight Technology), but there's no way to measure it. How do I do that?


Fill with oil until it starts to come out of the lower overflow tube. More details can be found in the repair manual (Etzold).