This option is not supported via admin panel. You will need to edit \wp-content\themes\myhome\assets\js\myhome.min.js file

1. find: 

autoplayTimeout:4e3

2. change to

autoplayTimeout:2500

3. Visit your website and clear browser cache (e.g. CTRL + F5 on Google Chrome) or try incognito mode. The new speed will be 2,5s