How can I improve my page speed by minifying Javascript?

Looks like most of the scripts in your screenshot are from apps and other 3rd party like Facebook. You cannot optimize these scripts, that would have to done by the app developers. All you can do there is to remove as many of these apps and marketing scripts from your site as you can. In some cases you may be able to control when and where these scripts are loaded on your site. There are some strategies to this, such as deferring scripts and lazy loading them some time after the initial page load or on some event like scroll or click.