When i change the speed of a clip i just get a freeze image. I'm using Version 0.9.6, KDE Development Platform 4.11.3
I hope someone can help me.

You've hit a long standing bug. Albeit said to be fixed, I still have problems using it even in recent svn versions from sunab's repo. I usually see corrupted frames, trailing froozen frames, and occasionally a crash as an added bonus.

You could try to remux the clip using the transcode options - had some success with it when having a frozen frame.

How can i do that and what options do i have to set?

Just as described here: http://userbase.kde.org/Kdenlive/Manual ... /Transcode

Requires that the video profile is compatible with your video track for the accelerated effect works.