diff --git a/Classes/DataProcessing/FlexFormProcessor.php b/Classes/DataProcessing/FlexFormProcessor.php
index 04762646..0f54b99c 100644
--- a/Classes/DataProcessing/FlexFormProcessor.php
+++ b/Classes/DataProcessing/FlexFormProcessor.php
@@ -14,6 +14,7 @@
  * The TYPO3 project - inspiring people to share!
  */
 
+use TYPO3\CMS\Core\Service\FlexFormService;
 use TYPO3\CMS\Core\Utility\GeneralUtility;
 use TYPO3\CMS\Frontend\ContentObject\ContentObjectRenderer;
 use TYPO3\CMS\Frontend\ContentObject\DataProcessorInterface;
@@ -56,7 +57,7 @@ public function process(ContentObjectRenderer $cObj, array $contentObjectConfigu
         $fieldName = $cObj->stdWrapValue('fieldName', $processorConfiguration, 'pi_flexform');
 
         // parse flexform
-        $flexformService = GeneralUtility::makeInstance('TYPO3\\CMS\\Extbase\\Service\\FlexFormService');
+        $flexformService = GeneralUtility::makeInstance(FlexFormService::class);
         $processedData[$targetVariableName] = $flexformService->convertFlexFormContentToArray($cObj->data[$fieldName]);
 
         // if targetvariable is settings, try to merge it with contentObjectConfiguration['settings.']
diff --git a/Classes/Utility/FixedPostVarsConfigurationUtility.php b/Classes/Utility/FixedPostVarsConfigurationUtility.php
index 527ebb5d..92289499 100644
--- a/Classes/Utility/FixedPostVarsConfigurationUtility.php
+++ b/Classes/Utility/FixedPostVarsConfigurationUtility.php
@@ -3,6 +3,7 @@
 namespace T3kit\themeT3kit\Utility;
 
 use Doctrine\DBAL\Query\QueryBuilder;
+use Psr\Log\LoggerAwareTrait;
 use TYPO3\CMS\Backend\Utility\BackendUtility;
 use TYPO3\CMS\Core\Database\ConnectionPool;
 use TYPO3\CMS\Core\Database\DatabaseConnection;
@@ -16,6 +17,7 @@
  */
 class FixedPostVarsConfigurationUtility
 {
+    use LoggerAwareTrait;
 
     /**
      * Update configuration file of fixed post vars
@@ -27,9 +29,8 @@ public function updateConfiguration()
         $filePath = $this->getSaveFilePath();
 
         if (!$this->canWriteConfiguration($filePath)) {
-            throw new \RuntimeException(
-                $filePath . ' is not writable.',
-                1485349703
+            $this->logger->error(
+                'Could not write realurl configuration to file "' . $filePath . '"'
             );
         }
 
@@ -146,35 +147,23 @@ protected function getFixedPagesUids()
     {
         $field = 'tx_themet3kit_fixed_post_var_conf';
 
-        if (version_compare(TYPO3_version, '8.0', '<')) {
-            /** @var DatabaseConnection $dbConnection */
-            $dbConnection = $GLOBALS['TYPO3_DB'];
-
-            $pages = $dbConnection->exec_SELECTgetRows(
-                'uid, ' . $field,
-                'pages',
-                $field . ' != \'0\' AND ' . $field . ' != \'\''
-                . BackendUtility::deleteClause('pages')
-            );
-        } else {
-            /** @var QueryBuilder $queryBuilder */
-            $queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)->getQueryBuilderForTable('pages');
-            $pages = $queryBuilder
-                ->select('uid', 'tx_themet3kit_fixed_post_var_conf')
-                ->from('pages')
-                ->where(
-                    $queryBuilder->expr()->neq(
-                        $field,
-                        $queryBuilder->createNamedParameter('')
-                    ),
-                    $queryBuilder->expr()->neq(
-                        $field,
-                        $queryBuilder->createNamedParameter('0')
-                    )
+        /** @var QueryBuilder $queryBuilder */
+        $queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)->getQueryBuilderForTable('pages');
+        $pages = $queryBuilder
+            ->select('uid', 'tx_themet3kit_fixed_post_var_conf')
+            ->from('pages')
+            ->where(
+                $queryBuilder->expr()->neq(
+                    $field,
+                    $queryBuilder->createNamedParameter('')
+                ),
+                $queryBuilder->expr()->neq(
+                    $field,
+                    $queryBuilder->createNamedParameter('0')
                 )
-                ->execute()
-                ->fetchAll();
-        }
+            )
+            ->execute()
+            ->fetchAll();
 
         return $pages;
     }
diff --git a/Classes/Utility/HelperUtility.php b/Classes/Utility/HelperUtility.php
index 4da960b5..923ec7b5 100644
--- a/Classes/Utility/HelperUtility.php
+++ b/Classes/Utility/HelperUtility.php
@@ -3,10 +3,11 @@
 
 namespace T3kit\themeT3kit\Utility;
 
+use TYPO3\CMS\Core\Configuration\ExtensionConfiguration;
 use TYPO3\CMS\Core\Messaging\FlashMessage;
 use TYPO3\CMS\Core\Messaging\FlashMessageQueue;
 use TYPO3\CMS\Core\Utility\GeneralUtility;
-use TYPO3\CMS\Lang\LanguageService;
+use TYPO3\CMS\Core\Localization\LanguageService;
 
 /**
  * Class MainUtility
@@ -29,11 +30,7 @@ class HelperUtility
     public static function getExtConf()
     {
         if (self::$extConf === null) {
-            if (isset($GLOBALS['TYPO3_CONF_VARS']['EXT']['extConf']['theme_t3kit'])) {
-                self::$extConf = unserialize((string)$GLOBALS['TYPO3_CONF_VARS']['EXT']['extConf']['theme_t3kit']);
-            } else {
-                self::$extConf = [];
-            }
+            self::$extConf = GeneralUtility::makeInstance(ExtensionConfiguration::class)->get('theme_t3kit') ?: [];
         }
 
         return self::$extConf;
diff --git a/Classes/ViewHelpers/ContentEditableViewHelper.php b/Classes/ViewHelpers/ContentEditableViewHelper.php
index 15f82c1d..712a919b 100644
--- a/Classes/ViewHelpers/ContentEditableViewHelper.php
+++ b/Classes/ViewHelpers/ContentEditableViewHelper.php
@@ -14,7 +14,7 @@
  * The TYPO3 project - inspiring people to share!
  */
 
-use TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper;
+use TYPO3Fluid\Fluid\Core\ViewHelper\AbstractViewHelper;
 use TYPO3Fluid\Fluid\Core\Rendering\RenderingContextInterface;
 use TYPO3Fluid\Fluid\Core\ViewHelper\Traits\CompileWithRenderStatic;
 
diff --git a/Classes/ViewHelpers/Link/TelViewHelper.php b/Classes/ViewHelpers/Link/TelViewHelper.php
index 46280d53..9b7eec24 100644
--- a/Classes/ViewHelpers/Link/TelViewHelper.php
+++ b/Classes/ViewHelpers/Link/TelViewHelper.php
@@ -14,6 +14,8 @@
  * The TYPO3 project - inspiring people to share!
  */
 
+use TYPO3Fluid\Fluid\Core\ViewHelper\AbstractTagBasedViewHelper;
+
 /**
  * Tel link view helper.
  * Generates an tel link
@@ -28,7 +30,7 @@
  * <a href="tel:+464001234567">+46 (0) 40-01 ma 23 45 67</a>
  * </output>
  */
-class TelViewHelper extends \TYPO3\CMS\Fluid\Core\ViewHelper\AbstractTagBasedViewHelper
+class TelViewHelper extends AbstractTagBasedViewHelper
 {
     /**
      * @var string
diff --git a/Classes/ViewHelpers/RegisterViewHelper.php b/Classes/ViewHelpers/RegisterViewHelper.php
index 749ae501..30375859 100644
--- a/Classes/ViewHelpers/RegisterViewHelper.php
+++ b/Classes/ViewHelpers/RegisterViewHelper.php
@@ -14,8 +14,7 @@
  * The TYPO3 project - inspiring people to share!
  */
 
-use TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper;
-use TYPO3\CMS\Fluid\Core\ViewHelper\Facets\CompilableInterface;
+use TYPO3Fluid\Fluid\Core\ViewHelper\AbstractViewHelper;
 use TYPO3Fluid\Fluid\Core\Rendering\RenderingContextInterface;
 use TYPO3Fluid\Fluid\Core\ViewHelper\Traits\CompileWithRenderStatic;
 
@@ -26,7 +25,7 @@
  * @subpackage
  * @author Markus Goldbach <markus.goldbach@dkd.de>
  */
-class RegisterViewHelper extends AbstractViewHelper implements CompilableInterface
+class RegisterViewHelper extends AbstractViewHelper
 {
     use CompileWithRenderStatic;
 
diff --git a/Classes/ViewHelpers/Render/SvgViewHelper.php b/Classes/ViewHelpers/Render/SvgViewHelper.php
index 1acd4ab0..12795e5d 100644
--- a/Classes/ViewHelpers/Render/SvgViewHelper.php
+++ b/Classes/ViewHelpers/Render/SvgViewHelper.php
@@ -1,6 +1,8 @@
 <?php
 namespace T3kit\themeT3kit\ViewHelpers\Render;
 
+use TYPO3Fluid\Fluid\Core\ViewHelper\AbstractViewHelper;
+
 /***************************************************************
  *
  *  Copyright notice
@@ -25,7 +27,7 @@
  *
  *  This copyright notice MUST APPEAR in all copies of the script!
  ***************************************************************/
-class SvgViewHelper extends \TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper
+class SvgViewHelper extends AbstractViewHelper
 {
 
     /**