Debut has a setting to change the height of the Slideshow but not the width.
This is called Slide Height under the Slideshow section of the home page.
You can also edit the amount of products show in the collection page/list.
Changing this will change the size of the products thumbnails
i thank you for your reply to my issues ,
1. the problem with the slideshow is that when you swith to mobile view it does not adopt to it and it shows the slides out of the view.
2. about the thumbnail view in the product list , i need to increase the size of the thumbnail by at least 10% or 20 % .