frontoffice is working but backoffice is not working.

[Yenibosnaweb]

I got following error on the admin panel after 1 click upgrade.  from 1.7.5.0 to 8.1.7
frontoffice is working but backoffice is not working.

does anyone help me? 

https://tlemse.com/tlemse/

I will pay for the solution.

Fatal error: Uncaught Error: Call to undefined function Symfony\Bundle\FrameworkBundle\DependencyInjection\get_cfg_var() in /home/tlemse/public_html/vendor/symfony/symfony/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php:230 Stack trace: #0 /home/tlemse/public_html/vendor/symfony/symfony/src/Symfony/Component/DependencyInjection/Compiler/MergeExtensionConfigurationPass.php(76): Symfony\Bundle\FrameworkBundle\DependencyInjection\FrameworkExtension->load(Array, Object(Symfony\Component\DependencyInjection\Compiler\MergeExtensionConfigurationContainerBuilder)) #1 /home/tlemse/public_html/vendor/symfony/symfony/src/Symfony/Component/HttpKernel/DependencyInjection/MergeExtensionConfigurationPass.php(39): Symfony\Component\DependencyInjection\Compiler\MergeExtensionConfigurationPass->process(Object(Symfony\Component\DependencyInjection\ContainerBuilder)) #2 /home/tlemse/public_html/vendor/symfony/symfony/src/Symfony/Component/DependencyInjection/Compiler/Compiler.php(94): Symfony\Component\HttpKernel\DependencyInjection\MergeExtensionConfigurationPass->process(Object(Symfony\Component\DependencyInjection\ContainerBuilder)) #3 /home/tlemse/public_html/vendor/symfony/symfony/src/Symfony/Component/DependencyInjection/ContainerBuilder.php(762): Symfony\Component\DependencyInjection\Compiler\Compiler->compile(Object(Symfony\Component\DependencyInjection\ContainerBuilder)) #4 /home/tlemse/public_html/vendor/symfony/symfony/src/Symfony/Component/HttpKernel/Kernel.php(594): Symfony\Component\DependencyInjection\ContainerBuilder->compile() #5 /home/tlemse/public_html/vendor/symfony/symfony/src/Symfony/Component/HttpKernel/Kernel.php(136): Symfony\Component\HttpKernel\Kernel->initializeContainer() #6 /home/tlemse/public_html/app/AppKernel.php(96): Symfony\Component\HttpKernel\Kernel->boot() #7 /home/tlemse/public_html/vendor/symfony/symfony/src/Symfony/Component/HttpKernel/Kernel.php(196): AppKernel->boot() #8 /home/tlemse/public_html/tlemse/index.php(88): Symfony\Component\HttpKernel\Kernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, false) #9 {main} thrown in /home/tlemse/public_html/vendor/symfony/symfony/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php on line 230

[Prestashop Addict]

Delete folder var/cache/prod and dev