Why can't I move a game to the sd card? I read that you cannot move system apps or apps that have widgets to SD card.
This game doesn't provide a widget.

Is there anything I can do to make it move to SD ? Maybe fix something in apk ?

Storage:
Application 8,32 MB
Data 44,00 KB
NOTE: Never put system apps or apps including widgets (if you are using the widgets) to external storage. This can make them misbehave or even force close.


Download Android platform tools here
Turn on USB debugging on your phone and connect it to your pc (make sure the drivers are installed)
Extract the zip file to a directory of choice (on your pc)
Open cmd on your pc (assuming you're using Windows) and navigate using cd to where you extracted your platform-tools
When you have navigated to the folder using cmd type 


  adb devices


Check if you see your device on there, it should look something like this: 

If you can see your device on the list then move on to the next step. If not your drivers are not installed and you need to install them from your manufacturers website
Now type
Android 4.1 and above:


  adb shell pm get-install-location


Android 4.0 and below:


  adb shell pm setInstallLocation 2


This should return either auto or phone. We need to change this.
Now type
Android 4.1 and above:


  adb shell pm set-install-location 2  


Android 4.0 and below:


  adb shell pm setInstallLocation 2



This will switch it from auto to external.


Complete! Now you should be able to move apps to sdcard.


Sources:
http://techgage.com/article/moving_your_non-movable_android_apps_to_an_sd_card/