you can use a GP Page Header and add any Slider or other content Short Code within its Content area. Then assign this to your Blog page.
Here is the page header documentation:
I just want that on homepage. And not on posts/pages.
i am a little new to wordpress. On blogger there used to be a simple drag and drop widget. But in wordpress i don’t see an option to place a widget/slider/code on home page, Above the posts
I think the Page Header method that David mentioned is your best bet.
You can create a new Page Header, and add a widget area into the content area. If you use a plugin like this, you can add a widget area to the Page Header using a shortcode: https://wordpress.org/plugins/widget-shortcode/