The slider on the top front page of the Luviana theme displays the Child pages of the Home page.
You can find them under your dashboard > Pages > find the Home/Front Page and the pages below are the child pages.
Open the needed page and in the Featured Image section on the right (see the screenshot) you can replace/remove the image.
In case you want to display only the Home page featured image without child pages slides, you would need to delete child pages or remove their "parent" page to be "Home" page.
In this way, there will be displayed only the featured image of the Home page, without slides (child pages).
Also, if needed, you may reduce the height of slider on front page adding the style below to Appearance > Customize > Additional CSS
padding:3.5rem 15px 8.625rem !important;
In order to change the button text, you should go to edit the child page of Home Page and edit the text of Read More tag:
By the way, since the 1.2.0 Luviana theme version, there was added the ability to set up video as a first slide for front-page slideshow.
It is possible to enable or disable slideshow and video as a first slide under your dashboard > Appearance > Customize > Theme Options > Front Page Slider.