Hi @felix,
I hope you are well today and thank you for your question.
Please make sure you have set the slider category to the posts which you want to display in the slider.
The slider by default displays 4 slides in the slider but you can increase the number of slides by using the custom child theme solution shared in the following topic.
https://colorlibsupport.com/t/slider-more-than-4-older-post-in-other-language-erase-date/#post-58829
Best Regards,
Movin