display a div on ervery site but not frontpage?

You need to tell the PHP to echo the div.

if (! is_front_page()) :
echo '<div class="button-kontakt"> <a href="https://wordpress.stackexchange.com/kontakt"><p>ANFRAGE</p></a></div>';
endif;

Unless you just want it on the top of the page, you need to add that code to a template file, not the functions file. If it is something that appears at the bottom of every page except the homepage, putting it in footer.php may be applicable.

Also, have you set the page you don’t want to see it on as the front page via the option in the Appearance->Customise menu?

Related Posts:

  1. Missing feature image link function
  2. How to customize the_archive_title()?
  3. How to override parent functions in child themes?
  4. Get menu object from theme_location
  5. Displaying the number of updates available in the Admin area
  6. Trying to use add_action and do_action with parameters
  7. When tax_query used, results disappear (0 =1 produced)
  8. Safe to disable wptexturize?
  9. Get a list of all available fields in the User Profile
  10. How do I use the WP image functions in a page template?
  11. How to remove Customize from admin menu bar after WP 4.3
  12. Targeting specific menu with wp_nav_menu_items
  13. why doesnt is_home() work in functions.php
  14. wp_get_attachment_image returns different image size
  15. Insert Ad Code in the Middle of a Post
  16. Enabling shortcodes for custom fields
  17. Passing variables to templates (alternatives to globalizing variables)
  18. Add options to featured image
  19. disable comments if array exists
  20. WordPress Change Post Templates,but not drop down, but Image selection
  21. Programmatically Add Font-Awesome Icons to Category Widget
  22. Remove images from get_the_excerpt
  23. Remove “says” from comments
  24. Reuse variable in hook callback
  25. Dynamically Register Sidebars For Each Top Level Page
  26. Run Product Filter Javascript On Page Template
  27. What is the criteria for pluggable functions?
  28. Can you use admin pages functionality on the frontend of your site
  29. How to add a column to the Trash page?
  30. Theme-Config tab in admin Pannel?
  31. Display more recent and less recent posts in same category
  32. Overwrite Parent Theme add_image_size in Child Theme
  33. Custom registration URL lost when user makes signup mistake
  34. Images uploaded using media uploader are appearing upside down
  35. How to target only the front page (not subsequent paginated pages) in theme/plugin?
  36. Individually styling date month year [closed]
  37. Tiny MCE-modifications (plugins) stopped working in WordPress 5.6
  38. How to insert custom widget in custom sidebar in theme activation?
  39. Writing functions in WordPress functions.php that don’t replace a WordPress core function
  40. How to hook into a function offered by a plugin?
  41. Echo tags used to describe the theme
  42. HTTP_HOST changing in functions.php
  43. Change position of media in admin menu
  44. How to Display Frontend CSS for Administrator only
  45. How can I remove the main description text box in a Woocommerce product editor page? I only use the “Product short description” text box [closed]
  46. Automatically assign video ‘poster’ value to ‘filename’ for archive listing
  47. 404 redirect to previous category
  48. show first 3 thumbnails of posts in different sizes [closed]
  49. Getting custom image size URL in functions
  50. new_excerpt_more link not working properly
  51. Where to add the permalink in this function?
  52. WordPress function saves a post twice and updates all posts
  53. Change CSS for logged in users
  54. Always the Latest google jQuery instead of default WordPress jQuery
  55. if statement for wordpress default featured image on single post
  56. Function to display post by specific author
  57. Return category name with & Ampersand doesnt work
  58. Control the srcset much more (not all sizes in it each time)
  59. Warning: join(): Invalid arguments passed in post-template.php
  60. javascript and css links not working on sever
  61. is_page() or is_single not working
  62. What are the meta fields for an attachment?
  63. how to change “posted by” words
  64. WordPress wraps span tags into p tags
  65. WordPress can’t get jquery/unslider to work
  66. Replace admin header logo with an image
  67. how get number of twitter followers in wordpress
  68. template_redirect action only firing if logged in
  69. Unable to use get_page_by_title() more than once per page?
  70. Featured Image and Tags problem
  71. Advanced method to control cache of enqueued style/script
  72. How to require a config file in a template and in function.php?
  73. Issue passing action class to nested function. Admin Columns
  74. Populate Product Regular Price with a calculated ACF Field Value
  75. Header menu aligned right on all pages except for single-post page [closed]
  76. large image size of 1440×1440 not pulling 2x of 2880×2880 image
  77. How to make the RTL.css the dominant css code?
  78. Auto remove tags on certain date
  79. get_field() with ID in one signal filter not working
  80. Remove External Links from WordPress posts Using add_filter() in Theme functions.php
  81. I’m getting invalid taxonomy in init action
  82. Is there any requirements to do socket programming with WordPress?
  83. Only seems to be displaying one child when there are supposed to be multiple
  84. Rest API User Levels
  85. adding google analytics via echo or between tags
  86. Slider Thumbnail Size Issue [closed]
  87. same get_posts function works diffrently in tag.php and functions.php
  88. Call custom field using php
  89. WordPress permanently logging users out
  90. Meta Box value not been pulled in
  91. How to Update User Meta Field other than from profile?
  92. Retrieve array of attachment IDs attached to a given Post ID
  93. add_theme_support not outputting thumbnails
  94. More link – not text
  95. update_user_option not working as expected
  96. Shortcodes not outputting in correct divs
  97. How do I access variables outside a function [closed]
  98. Help finishing script to export WP user data when form submitted
  99. PHP Notice: Function is_page was called incorrectly. Conditional query tags do not work before the query is run. Before then, they always return false
  100. woocommerce_sort_product_tabs() expects an array
techhipbettruvabetnorabahisbahis forumutaraftarium24eduseduedusedusedueduedueduseduedu