Content/post box size on homepage is not the same

Hello,

I have an issue with my posts, namely when i post a content with a picture, on my homepage the size of the post-box is not the same (on some posts is longer), which is not looking good.

I tried to change the image dimensions in order to fix it, but no such luck. So, how can i fix this issue for all my web-posts? Can i put fixed dimensions for my after-post-content on my homepage?

Thanks in advance