Zend certified PHP/Magento developer

Exeption: “attribute ‘remove’ is not allowed.” in developer mode

When i enable the developer mode on my Magento 2.3.3 instance i get the following error message when calling category pages in webbrowser:

Exception #0 (MagentoFrameworkConfigDomValidationException): Element 'block', attribute 'remove': The attribute 'remove' is not allowed.
Line: 976

Element 'block', attribute 'remove': The attribute 'remove' is not allowed.
Line: 980


Exception #0 (MagentoFrameworkConfigDomValidationException): Element 'block', attribute 'remove': The attribute 'remove' is not allowed.
Line: 976

Element 'block', attribute 'remove': The attribute 'remove' is not allowed.
Line: 980

#1 MagentoFrameworkConfigDom->__construct() called at [vendor/magento/framework/ObjectManager/Factory/AbstractFactory.php:116]
#2 MagentoFrameworkObjectManagerFactoryAbstractFactory->createObject() called at [vendor/magento/framework/ObjectManager/Factory/Dynamic/Developer.php:66]
#3 MagentoFrameworkObjectManagerFactoryDynamicDeveloper->create() called at [vendor/magento/framework/ObjectManager/ObjectManager.php:56]
#4 MagentoFrameworkObjectManagerObjectManager->create() called at [vendor/magento/framework/Config/DomFactory.php:43]
#5 MagentoFrameworkConfigDomFactory->createDom() called at [vendor/magento/framework/View/Model/Layout/Update/Validator.php:141]
#6 MagentoFrameworkViewModelLayoutUpdateValidator->isValid() called at [vendor/magento/framework/View/Model/Layout/Merge.php:494]
#7 MagentoFrameworkViewModelLayoutMerge->_validateMergedLayout() called at [vendor/magento/framework/View/Model/Layout/Merge.php:470]
#8 MagentoFrameworkViewModelLayoutMerge->load() called at [generated/code/Magento/Framework/View/Model/Layout/Merge/Interceptor.php:193]
#9 MagentoFrameworkViewModelLayoutMergeInterceptor->load() called at [vendor/magento/framework/View/Layout/Builder.php:86]
#10 MagentoFrameworkViewLayoutBuilder->loadLayoutUpdates() called at [vendor/magento/framework/View/Layout/Builder.php:63]
#11 MagentoFrameworkViewLayoutBuilder->build() called at [vendor/magento/framework/View/Page/Config.php:224]
#12 MagentoFrameworkViewPageConfig->build() called at [vendor/magento/framework/View/Page/Config.php:587]
#13 MagentoFrameworkViewPageConfig->getElementAttribute() called at [vendor/magento/framework/View/Page/Config.php:545]
#14 MagentoFrameworkViewPageConfig->addBodyClass() called at [vendor/magento/module-catalog/Controller/Category/View.php:217]
#15 MagentoCatalogControllerCategoryView->execute() called at [vendor/magento/framework/Interception/Interceptor.php:58]
#16 MagentoCatalogControllerCategoryViewInterceptor->___callParent() called at [vendor/magento/framework/Interception/Interceptor.php:138]
#17 MagentoCatalogControllerCategoryViewInterceptor->MagentoFrameworkInterception{closure}() called at [vendor/magento/framework/Interception/Interceptor.php:153]
#18 MagentoCatalogControllerCategoryViewInterceptor->___callPlugins() called at [generated/code/Magento/Catalog/Controller/Category/View/Interceptor.php:26]
#19 MagentoCatalogControllerCategoryViewInterceptor->execute() called at [vendor/magento/framework/App/Action/Action.php:108]
#20 MagentoFrameworkAppActionAction->dispatch() called at [vendor/magento/framework/Interception/Interceptor.php:58]
#21 MagentoCatalogControllerCategoryViewInterceptor->___callParent() called at [vendor/magento/framework/Interception/Interceptor.php:138]
#22 MagentoCatalogControllerCategoryViewInterceptor->MagentoFrameworkInterception{closure}() called at [vendor/magento/framework/Interception/Interceptor.php:153]
#23 MagentoCatalogControllerCategoryViewInterceptor->___callPlugins() called at [generated/code/Magento/Catalog/Controller/Category/View/Interceptor.php:39]
#24 MagentoCatalogControllerCategoryViewInterceptor->dispatch() called at [vendor/magento/framework/App/FrontController.php:159]
#25 MagentoFrameworkAppFrontController->processRequest() called at [vendor/magento/framework/App/FrontController.php:99]
#26 MagentoFrameworkAppFrontController->dispatch() called at [vendor/magento/framework/Interception/Interceptor.php:58]
#27 MagentoFrameworkAppFrontControllerInterceptor->___callParent() called at [vendor/magento/framework/Interception/Interceptor.php:138]
#28 MagentoFrameworkAppFrontControllerInterceptor->MagentoFrameworkInterception{closure}() called at [vendor/magento/module-store/App/FrontController/Plugin/RequestPreprocessor.php:94]
#29 MagentoStoreAppFrontControllerPluginRequestPreprocessor->aroundDispatch() called at [vendor/magento/framework/Interception/Interceptor.php:135]
#30 MagentoFrameworkAppFrontControllerInterceptor->MagentoFrameworkInterception{closure}() called at [vendor/magento/module-page-cache/Model/App/FrontController/BuiltinPlugin.php:69]
#31 MagentoPageCacheModelAppFrontControllerBuiltinPlugin->aroundDispatch() called at [vendor/magento/framework/Interception/Interceptor.php:135]
#32 MagentoFrameworkAppFrontControllerInterceptor->MagentoFrameworkInterception{closure}() called at [vendor/magento/framework/Interception/Interceptor.php:153]
#33 MagentoFrameworkAppFrontControllerInterceptor->___callPlugins() called at [generated/code/Magento/Framework/App/FrontController/Interceptor.php:26]
#34 MagentoFrameworkAppFrontControllerInterceptor->dispatch() called at [vendor/magento/framework/App/Http.php:137]
#35 MagentoFrameworkAppHttp->launch() called at [generated/code/Magento/Framework/App/Http/Interceptor.php:24]
#36 MagentoFrameworkAppHttpInterceptor->launch() called at [vendor/magento/framework/App/Bootstrap.php:261]
#37 MagentoFrameworkAppBootstrap->run() called at [pub/index.php:40]

Im using a child theme based on the porto theme. My app/design/frontend/Smartwave/porto_child/Magento_Catalog/layout/catalog_category_view.xml looks as follows:

< ?xml version="1.0"?>


    
        
             
        
        
            
            
        
        
        
            
        
    
    

My app/design/frontend/Smartwave/porto_child/Magento_Catalog/layout/catalog_product_view.xml looks as follows:

< ?xml version="1.0"?>


    
        
    
    

        
        
        
        
            
        
        
            
        
        
        
    

I tried with this code to change the layout statements in catalog_product_view.xml to remove the blocks:

< ?xml version="1.0"?>


    
        
             
        
        
            
            
        
        
        
            
        
    
    

How can I get rid of the error messages, what have I missed?