This is the error:

Compile LESS to CSS failed
exception 'Exception' with message 'parse error: failed at `(~".span@{index}") { .span(@index); } ` line: 1570' in
/www/htdocs/w0125409/davidmacke.de/joomla/libraries/vendor/leafo/lessphp/lessc.inc.php:3553 Stack trace: #0 /www/htdocs/w0125409/davidmacke.de/joomla/libraries/vendor/leafo/lessphp/lessc.inc.php(2364): lessc_parser->throwError() #1 /www/htdocs/w0125409/davidmacke.de/joomla/libraries/vendor/leafo/lessphp/lessc.inc.php(1887): lessc_parser->parse('//\n// Variables...') #2
/www/htdocs/w0125409/davidmacke.de/joomla/plugins/system/t3/includes/lessphp/legacy.less.php(285): lessc->compile('//\n// Variables...') #3
/www/htdocs/w0125409/davidmacke.de/joomla/plugins/system/t3/includes/lessphp/legacy.less.php(560): T3Less->compileCss('templates/newli...', 'templates/newli...') #4
/www/htdocs/w0125409/davidmacke.de/joomla/plugins/system/t3/includes/core/action.php(63): T3Less::compileAll('david-macke') #5
/www/htdocs/w0125409/davidmacke.de/joomla/plugins/system/t3/includes/core/action.php(40): T3Action::lesscall() #6
/www/htdocs/w0125409/davidmacke.de/joomla/plugins/system/t3/includes/core/t3.php(176): T3Action::run('lesscall') #7
/www/htdocs/w0125409/davidmacke.de/joomla/plugins/system/t3/t3.php(109): T3::checkAction() #8 [internal function]: plgSystemT3->onAfterRoute() #9
/www/htdocs/w0125409/davidmacke.de/joomla/libraries/joomla/event/event.php(69): call_user_func_array(Array, Array) #10
/www/htdocs/w0125409/davidmacke.de/joomla/libraries/joomla/event/dispatcher.php(160): JEvent->update(Array) #11
/www/htdocs/w0125409/davidmacke.de/joomla/libraries/joomla/application/base.php(106): JEventDispatcher->trigger('onAfterRoute', NULL) #12 /www/htdocs/w0125409/davidmacke.de/joomla/libraries/cms/application/administrator.php(461): JApplicationBase->triggerEvent('onAfterRoute') #13
/www/htdocs/w0125409/davidmacke.de/joomla/libraries/cms/application/administrator.php(137): JApplicationAdministrator->route() #14
/www/htdocs/w0125409/davidmacke.de/joomla/libraries/cms/application/cms.php(257): JApplicationAdministrator->doExecute() #15
/www/htdocs/w0125409/davidmacke.de/joomla/administrator/index.php(51): JApplicationCms->execute() #16 {main}

can you help me please...

It appears when we start "less to css" in template backend.

Here is your joomla-login:

/* Removed for security reasons */

Hi

I'm going to delete the details above as this is a live forum and create a ticket for you