linux - Switching left alt and left win

I have a Thinkpad X230 (german layout, [edit]running linux[/edit]) and I want to switch the left win- and the left alt-key somehow with the right alt-key (AltGr) not being touched.

However, I haven't found a working solution yet. I know the question dealing with exactely this problem here on superuser (How do I swap Alt and Windows keys with xmodmap?), but the xmodmaps there just give me an error:

X Error of failed request: BadValue (integer parameter out of range for operation)

Major opcode of failed request: 118 (X_SetModifierMapping)

Value in failed request: 0x17

Serial number of failed request: 13

Current serial number in output stream: 13

And as the Keyboardmodel is a different one, I don't know which setxkbmap-command is required.

What I tried so far (besides the Xmodmaps in the question mentioned above) is
* "setxkbmap -option altwin:swap_lalt_lwin", which does exactely nothing
* some xmodmap-variations (unfortunately I do not remember which combinations I tried, however, I wasn't able to make it work), my last status with most of my used commands is this one:

!!Clear Super & Alt

!clear Mod1

!clear Mod4

!remove mod1 = Alt_L

!remove mod4 = Super_L

!keycode 204 = NoSymbol NoSymbol NoSymbol NoSymbol

!keycode 205 = NoSymbol NoSymbol NoSymbol NoSymbol

!keycode 206 = NoSymbol NoSymbol NoSymbol NoSymbol

!keycode 207 = NoSymbol NoSymbol NoSymbol NoSymbol

!

!keycode 64 = Super_L Super_L Super_L Super_L

!keycode 133 = Alt_L Alt_L Alt_L Alt_L

!keysym Alt_L = Super_L

!keysym Super_L = Alt_L

!Remap Super & Alt

!add mod1 = Super_L

!add mod4 = Alt_L

Is someone experienced in using xmodmap or setxkbmap and can me help out? It would be very appreciated!

Thanks in advance!