Image size of portfolio items

Hi, there,

I wonder whether it is possible to change the image size of portfolio items. I have some services pages on my website that are created as portfolio items. Can the images be made a bit smaller in the non-mobile views than they currently are? (The mobile view is perfect and needs no change.)

In addition, I would also like to know if the title/heading of such pages could be put on top of the image (instead of below it).

Here is a link to one of the service pages:
http://primeed.net/portfolio/executive-training-english/

Thank you a lot!

Best,
Renee