How to turn off Samsung Galaxy a3 if the screen doesnt work? How do I turn it off? My screen is not broken it just stopped working and i tried to restart it by pressing the on/off button and volume down-button but it didnt work.

Thanks for you if you can help me!
If you know what adb is and how to use it, you can run adb shell reboot -p

If not, you can install the following drivers, and extract the following zip file anywhere. Once done, enable USB debugging, plug your phone in your computer, and double-click on adbprompt.bat. You're going to see the following text in a command prompt:

Portable ADB Interface - v0.2 Public BETA
Packaged by Kickface of xda-developers forums

adb


Simply type shell reboot -p. When done, close the window.

For the sake of simplicity, you can, if you want, remove the battery instead. Generally it doesn't break anything.