Can't load my Homepage anymore

Hi,
after updating to Joomla4 my Website isn't reachable anymore.
Following errors occure with an hint concerning JEVENT (jevtimelimit):

0
Call to undefined method Joomla\CMS\Application\SiteApplication::isAdmin()
ERROR 0 - Call to undefined method Joomla\CMS\Application\SiteApplication::isAdmin() in /mnt/web413/b2/73/59121473/htdocs/joomla_02/plugins/jevents/jevtimelimit/jevtimelimit.php:18

Here some more Details:
Call stack
# Function Location
1 () JROOT/plugins/jevents/jevtimelimit/jevtimelimit.php:18
2 require_once() JROOT/libraries/src/Extension/ExtensionManagerTrait.php:214
3 Joomla\CMS\Application\CMSApplication->loadPluginFromFilesystem() JROOT/libraries/src/Extension/ExtensionManagerTrait.php:157
4 Joomla\CMS\Application\CMSApplication->loadExtension() JROOT/libraries/src/Extension/ExtensionManagerTrait.php:96
5 Joomla\CMS\Application\CMSApplication->bootPlugin() JROOT/libraries/src/Plugin/PluginHelper.php:221
6 Joomla\CMS\Plugin\PluginHelper::import() JROOT/libraries/src/Plugin/PluginHelper.php:181
7 Joomla\CMS\Plugin\PluginHelper::importPlugin() JROOT/components/com_jevents/router.php:89
8 JEventsBuildRoute() JROOT/libraries/src/Component/Router/RouterLegacy.php:71
9 Joomla\CMS\Component\Router\RouterLegacy->build() JROOT/libraries/src/Router/SiteRouter.php:441
10 Joomla\CMS\Router\SiteRouter->buildSefRoute() JROOT/libraries/src/Router/Router.php:405
11 Joomla\CMS\Router\Router->processBuildRules() JROOT/libraries/src/Router/Router.php:192
12 Joomla\CMS\Router\Router->build() JROOT/libraries/src/Router/Route.php:141
13 Joomla\CMS\Router\Route::link() JROOT/libraries/src/Router/Route.php:93
14 Joomla\CMS\Router\Route::_() JROOT/modules/mod_menu/src/Helper/MenuHelper.php:154
15 Joomla\Module\Menu\Site\Helper\MenuHelper::getList() JROOT/libraries/astroid/framework/library/astroid/Component/Menu.php:581
16 Astroid\Component\Menu::getMobileMenu() JROOT/libraries/astroid/framework/frontend/mobilemenu.php:45
17 include() JROOT/libraries/src/Layout/FileLayout.php:128
18 Joomla\CMS\Layout\FileLayout->render() JROOT/libraries/astroid/framework/library/astroid/Document.php:83
19 Astroid\Document->include() JROOT/libraries/astroid/framework/frontend/document/body.php:51
20 include() JROOT/libraries/src/Layout/FileLayout.php:128
21 Joomla\CMS\Layout\FileLayout->render() JROOT/libraries/astroid/framework/library/astroid/Document.php:83
22 Astroid\Document->include() JROOT/templates/tp_ice/index.php:32
23 require() JROOT/libraries/src/Document/HtmlDocument.php:736
24 Joomla\CMS\Document\HtmlDocument->_loadTemplate() JROOT/libraries/src/Document/HtmlDocument.php:791
25 Joomla\CMS\Document\HtmlDocument->_fetchTemplate() JROOT/libraries/src/Document/HtmlDocument.php:608
26 Joomla\CMS\Document\HtmlDocument->parse() JROOT/libraries/src/Application/CMSApplication.php:1004
27 Joomla\CMS\Application\CMSApplication->render() JROOT/libraries/src/Application/SiteApplication.php:714
28 Joomla\CMS\Application\SiteApplication->render() JROOT/libraries/src/Application/CMSApplication.php:299
29 Joomla\CMS\Application\CMSApplication->execute() JROOT/includes/app.php:61
30 require_once() JROOT/index.php:32

What is here the problem?