@fishcoder
Hello Nadine
Had the same problem, for which I have now found the solution through trial and error.

You only must make changes in input.xml

First, however, you must configure the controller correctly in the main menu.

make sure that you assign the second joystick as follows:
up = C-Button Down
left = C-Button Right

Also:
x = C-Button UP
y = C-Button Left

Then edit the input.xml file as follows:

<inputList>
<input name="AnalogDeadzone" value="4096,4096" />
<input name="AnalogPeak"     value="32768,32768" />
<input name="a"        	     value="A Button" />
<input name="b"        	     value="B Button" />
<input name="x"        	     value="C Button U" />
<input name="y"        	     value="C Button L" />
<input name="start"    	     value="Start" />
<input name="select"   	     value="" />
<input name="l1"   		     value="L Trig" />
<input name="r1"	 	     value="R Trig" />
<input name="l2"       	     value="Z Trig" />
<input name="r2"       	     value="" />
<input name="l3"             value="Mempak switch" />
<input name="r3"             value="Rumblepak switch" />
<input name="up"       	     value="DPad U" />
<input name="down"     	     value="DPad D" />
<input name="right"    	     value="DPad R" />
<input name="left"     	     value="DPad L" />
<input name="joystick1up"    value="Y Axis" />
<input name="joystick1down"  value="Y Axis" />
<input name="joystick1left"  value="X Axis" />
<input name="joystick1right" value="X Axis" />
<input name="joystick2up"    value="C Button D" />
<input name="joystick2down"  value="" />
<input name="joystick2left"  value="C Button R" />
<input name="joystick2right" value="" />
</inputList>

then it should work.

Cheers, Ben