I want to wait a moment (.5 seconds) before I increase the sound, how can i achieve this without using Thread.sleep, because i want my game to keep runnig.
You can either use a java timer approach: http://developer.android.com/reference/java/util/Timer.html
Or you could simply keep track of the time elapsed since the increase volume action began. Maybe something like this in your render method or somewhere else:
Of course you need to set volumeIncreasing to true and actionBeginTime=System.nanoTime() somewhere when the action begins.