TYPO3 Core

I have downloaded a t3x file from TYPO3 4.7 and imported it in current GIT-Version (30.10.2013). This results in following error:

Extension Upload failed
Package "jw_api" is not available. Please check if the package exists and that the package key is correct (package keys are case sensitive).

I can see my ext in typo3conf/ext, but it was not listed in Extension Manager. I have removed this directory and tried again, because I have to copy the error message for this issue. After reloading the Extension Manager it results in this Errormessage:

exec_INSERTquery
caller TYPO3\CMS\Core\Database\DatabaseConnection::exec_INSERTquery
ERROR Duplicate entry '193' for key 'PRIMARY'
lastBuiltQuery INSERT INTO sys_file (creation_date,modification_date,size,identifier,storage,name,sha1,type,mime_type,extension,missing,uid,pid) VALUES ('1383122113','1383122113','369','/typo3conf/ext/jw_api/ext_icon.gif','0','ext_icon.gif','a5fb22d5805227f10d884294097408d6e577e8d9','2','image/gif','gif','0','193','0')
debug_backtrace TYPO3\CMS\Extbase\Core\ModuleRunner->callModule#47 // TYPO3\CMS\Extbase\Core\Bootstrap->run#81 // TYPO3\CMS\Extbase\Core\Bootstrap->handleRequest#197 // TYPO3\CMS\Extbase\Mvc\Web\BackendRequestHandler->handleRequest#208 // TYPO3\CMS\Extbase\Mvc\Dispatcher->dispatch#47 // TYPO3\CMS\Extbase\Mvc\Controller\ActionController->processRequest#83 // TYPO3\CMS\Extbase\Mvc\Controller\ActionController->callActionMethod#169 // TYPO3\CMS\Fluid\View\AbstractTemplateView->render#338 // TYPO3\CMS\Fluid\Core\Parser\ParsingState->render#200 // TYPO3\CMS\Fluid\Core\Parser\SyntaxTree\RootNode->evaluate#92 // TYPO3\CMS\Fluid\Core\Parser\SyntaxTree\AbstractNode->evaluateChildNodes#26 // TYPO3\CMS\Fluid\Core\Parser\SyntaxTree\ViewHelperNode->evaluate#47 // TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper->initializeArgumentsAndRender#132 // TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper->callRenderMethod#237 // call_user_func_array#255 // TYPO3\CMS\Fluid\ViewHelpers\Be\ContainerViewHelper->render# // TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper->renderChildren#136 // TYPO3\CMS\Fluid\Core\Parser\SyntaxTree\AbstractNode->evaluateChildNodes#285 // TYPO3\CMS\Fluid\Core\Parser\SyntaxTree\ViewHelperNode->evaluate#47 // TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper->initializeArgumentsAndRender#132 // TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper->callRenderMethod#237 // call_user_func_array#255 // TYPO3\CMS\Fluid\ViewHelpers\RenderViewHelper->render# // TYPO3\CMS\Fluid\View\AbstractTemplateView->renderSection#90 // FluidCache_Extensionmanager_List_action_index_76be66fb796cfc08e571e02a691aec83d74747ca->section_4f9be057f0ea5d2ba72fd2c810e8d7b9aa98b469#240 // TYPO3\CMS\Fluid\ViewHelpers\ForViewHelper::renderStatic#1563 // {closure}#122 // TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper->initializeArgumentsAndRender#1232 // TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper->callRenderMethod#237 // call_user_func_array#255 // TYPO3\CMS\Extensionmanager\ViewHelpers\ImageViewHelper->render# // TYPO3\CMS\Fluid\ViewHelpers\ImageViewHelper->render#79 // TYPO3\CMS\Frontend\ContentObject\ContentObjectRenderer->getImgResource#129 // TYPO3\CMS\Core\Resource\ResourceFactory->retrieveFileOrFolderObject#5316 // TYPO3\CMS\Core\Resource\ResourceFactory->getFileObjectFromCombinedIdentifier#447 // TYPO3\CMS\Core\Resource\ResourceFactory->getFileObjectByStorageAndIdentifier#378 // TYPO3\CMS\Core\Resource\Index\FileIndexRepository->add#396 // TYPO3\CMS\Core\Database\DatabaseConnection->exec_INSERTquery#168 // TYPO3\CMS\Core\Database\DatabaseConnection->debug#198