We need more informations.Please provide a copy of your 'System Info'. This can be get from the Photoshop menu item Help > System Info. There's a copy button in the System Info dialog. Press this button and paste the info into your next forum post.
What do you mean with "Rendern dauert viel zu lange."? What do your try to do? Which format does your video have? How long does it take to rendering?
Please note: Photoshop isn't the first choice to edit videos.
Is your system up-to-date? Do you have installed all recent updates and patches for the operating system and the device drivers, especially the graphic driver. If you have a NVidia graphic card installed, make sure that you are using the recent Studio version of the driver, not the Game Ready version.