Is it possible to slow down the slider?
Nope, sorry. It could be possible if you make your changes directly into main.js, than re-compress the file into main.min.js. But you’ll lose changes upon theme update.
Can you give me some detailed information about this?
I can, but it’s not a good idea to do this without a child theme. Open up /js/main.js, search for 4000 and replace both instances with the value you want in miliseconds. Then go to functions.php, search for
main.min.js and replace with