Thanks for the wonderful theme.
Please how can i change the header image height. I want it a bit shorter in length. I tried uploading a smaller image than suggested but it made no difference as the theme stretched it to fit the pre-loaded size.
Secondly, where do i change the “Proudly powered by WordPress…” on the footer?
Header is designed to cover entire viewport height. This is default theme functionality. You can change this bey changing theme folder / js / scripts.js file (first function is controlling this). Since this is default functionality, you have to change this by yourself or to contact for e.g. codeable if you are not familiar with programming.
Search a forum for copyright change. It is simple. Create child theme https://codex.wordpress.org/Child_Themes, copy footer.php file inside it (from main theme), and create modifications from there.