Installing Child Team

Hi, I just purchased enigma premium and the front (slide)photos are definitely too big. I would like to come back to the size and look of the photos like the enigma( simple one) has. I downloaded Child Theme and the zip but I was not able to instal the zip from the computer. Also I was trying hours to find out how to put the title on the sliding photos from the middle to the bottom. In addition I would like to add Polish language next to English for people to use. Is it possible?
One think more is it possible to change the color form the white one on the top (social media, names etc) to black ones then I would be able to change the color of the side for all white?
The name of the website: http://www.gosiadombaj.com
Thank you