Hello joerg,
Thank you so much for using out theme Education Base. This options for managing the slider time is only available on the premium theme. So, we recommend you to use the premium theme for it. If you want to do it on free version, you need to customize the theme. you can find the slider time code on assets/education-base-custom.js file.
Note: Child Theme is recommended to customize the theme.
Regards
Acme Supports