Home page blog picture too big

The pictures that i want featured i want to be in banner format, maybe 1500×600 in ratio or whatever looks good. I am talking about the pictures i have feautured on my new posts just don’t know how to change it, cropping it just makes it zoom in until it is at the same ratio.

Also:
https://gyazo.com/6cb7ba421bdec5c94e802b45615ccf1a
when hovering on one of the posts it displays the first letter of that blog. is there a possibility to change that letter to the text Read more?
(see link)

please keep in mind that my coding isn’t very good so not too much jargon haha

Thanks a lot,
Daniel

The page I need help with: [log in to see the link]