Hi Aki,
1. You can change that in the plugin settings here: https://i.imgur.com/CcHazTC.png
2. The issue is caused by a 3rd party script unfortunately, it is not normal scroll behavior. It captures and prevents inner element scrolling and propagates it to the body scroll. It is this smoothscroll.js script file, which is located at:
wp-content/themes/soledad/js/smoothscroll.js
So it seems to be coming from the theme. Try checking the theme settings to turn off “smooth scrolling” or something similar. Nowdays it is not recommended to fiddle with scrolling behavior either as devices can already handle that.