Thanks. Unfortunately It wasn’t the solution. “jetpack” was already added. If i deactivate the plugin you named, it is solved. 

Here is the text which is already filled in the field: 

analytics.js 

google-analytics

googletagmanager

analytics

gtag

url://stats.wp.com

_stq.push

browser-redirect/app.js

id:-js-extra

et_core_page_resource_fallback

window.$us === undefined

js-extra

fusionNavIsCollapsed

eio_lazy_vars

et_animation_data

wpforms_settings

var nfForms

//stats.wp.com

_stq.push

fluent_form_ff_form_instance_

cpLoadCSS

ninja_column_

var rbs_gallery_

var lepopup_

var billing_additional_field

var gtm4wp

var dataLayer_content

/ewww-image-optimizer/includes/load[_-]webp(\\.min)?.js

/ewww-image-optimizer/includes/check-webp(\\.min)?.js

ewww_webp_supported

/dist/js/browser-redirect/app.js

/perfmatters/js/lazyload.min.js

scripts.mediavine.com/tags/

initCubePortfolio

jetpack-lazy-images-js-enabled

jetpack-boost-critical-css

jetpack

Hello, there is a problem with the comment form on single post pages. Under the box „Type your comment here“ is [script_13] displayed (attachment shows it). It is visible when you go to homepage as a visitor. I can‘t see it in my wordpress dashboard. If i disable the comment form, the problem is solved.