RME - AIO sound card

How do i notice if the midi part in my RME - AIO sound card is half broken

Do you have the breakout cable? If not I’m not sure what you can do except check it shows in Cubase. If you do have the cable then connect a device with midi in and out and record and midi from the device and then play back to the device

The piano plug sounds good on its own and the drum module sounds also good on its own is there then nothing wrong with the midi part in my RME sound card

I don’t understand what you mean. The rme has midi in and out using a breakout cable. A vst plays from midi without using the output but to play a part in you use the input. What exactly are you trying to do and what is the problem?