[TYPO3-english] Re: Class 't3lib_extMgm' not found

[David Bruchmann]

Even I don't know exactly which extension you installed, in TER there is no compatible extension shown for TYPO3 version 7 or 8:

https://typo3.org/extensions/repository/?id=23&L=0&q=Image+slider&tx_solr%5Bfilter%5D%5BextensionMinTYPO3Version%5D=&tx_solr%5Bfilter%5D%5BextensionMaxTYPO3Version%5D=

To uninstall an extension and you don't have access to the backend anymore:
- open the file typo3conf/PackageStates.php
- search for the extension key
- change the line "state" => "active" below to "state" => "inactive", save the file.
- delete the folder typo3temp/Cache, don't worry, it will be created new automatically if it's missing.
- reload the backend-page
- now you should have access again, regrettable without the desired extension.