Hello
go to dashboard >> appearance >> theme editor >> there will style.css file to edit >> go to line no 22 and delete that line of code
you will see this code below in the line no 22 simply remove the display:none; code line from the code below
body::-webkit-scrollbar { display:none ; }

it should look like this after that
body::-webkit-scrollbar { }
then click on save button on the bottom.
let us know if it worked.
Thank you