Layout Change

Good evening!

I have a question regarding the layout of the page and the size of the featured images:

1.) Layout
I would like the newest post to be at the full width of the block (so basically a replacement of the slider) and with a bigger featured image than the older posts. Below that newest post I want the sidebar to begin, next to the older posts.

2.) Featured image
can I change the size of them to be bigger than 1018x460?

Thank you so much, it would be of great help!