but I can't, probably I am not doing the right things.
Sounds like. ;)
Give this a read.
Then create a directory like so
wp-content/themes/responsive-child and put this
style.css file in it verbatim:
Theme Name: Responsive Child Theme
Author: Self-Help WordPress User
/* Your CSS goes after here */
At this point do not copy any other files from the parent Responsive theme directory You will have all of the functions from the parent theme already. Never copy the
functions.php from the parent theme.
Activate the child theme and you can go from there.
Now that you're there already, what doesn't work that you want to change?
Edit: I blame the lack of coffee on my thinking this morning. Emil has also setup a dedicated forum for his themes.
That link is the support forum for Responsive Child Themes and posting there may get you a quicker response.