css – How to resize the post thumbnail on the home page

I would like to resize the thumbnails of the posts in my homepage in mobile view. I did it on desktop and tablet computers, but I can't do it on mobile devices. My website is www.aytepignosi.com. The thumbnails are now too small as can be seen in the screenshot. I would like to make them as they are in the desktop view, that means: the image automatically resized and centered according to the screen size. The CSS I used for the desktop is:

.post-body img {
display: block;

And also if this could apply to publication titles, again only for the home page in mobile view. When I open a post, everything seems fine.
Thanks in advance.
(I use blogger)
screenshot of home page posts