Hi @sabpaz,
I hope you are well today and thank you for your question.
There are two ways to resolve this.
The first one is you can use pages for the slider instead of posts by using the solution shared in the following topic.
https://colorlibsupport.com/t/using-pages-rather-than-posts-for-flexslider/
Please configure it as described in the below thread.
https://colorlibsupport.com/t/slider-for-pages/
The second one is by excluding slider posts from displaying in the blog. You can achieve this by developing custom code referring the solution posted in the below topic.
https://colorlibsupport.com/t/suppress-slider-on-posts-page/#post-24989
Best Regards,
Movin