Now the site doesn't show and we get the following Error on the home page

Exception: Notice: Use of undefined constant ICONV_IMPL – assumed
'ICONV_IMPL' in
/home/tassosco/public_html/vendor/magento/framework/Stdlib/StringUtils.php
on line 162 in
/home/tassosco/public_html/vendor/magento/framework/App/ErrorHandler.php:61
Stack trace: #0
/home/tassosco/public_html/vendor/magento/framework/Stdlib/StringUtils.php(162):
Magento\Framework\App\ErrorHandler->handler(8, 'Use of undefine…',
'/home/tassosco/…', 162, Array) #1
/home/tassosco/public_html/vendor/magento/framework/HTTP/Header.php(120):
Magento\Framework\Stdlib\StringUtils->cleanString('Mozilla/5.0
(X1…') #2
/home/tassosco/public_html/vendor/magento/framework/HTTP/Header.php(57):
Magento\Framework\HTTP\Header->_getHttpCleanValue('HTTP_USER_AGENT',
true) #3
/home/tassosco/public_html/vendor/magento/framework/App/Response/HeaderProvider/XssProtection.php(43):
Magento\Framework\HTTP\Header->getHttpUserAgent() #4
/home/tassosco/public_html/vendor/magento/framework/App/Response/HeaderManager.php(42):
Magento\Framework\App\Response\HeaderProvider\XssProtection->getValue()

5 /home/tassosco/public_html/vendor/magento/framework/Interception/Interceptor.php(123):

Magento\Framework\App\Response\HeaderManager->beforeSendResponse(Object(Magento\Framework\App\Response\Http\Interceptor))

6 /home/tassosco/public_html/var/generation/Magento/Framework/App/Response/Http/Interceptor.php(117):

Magento\Framework\App\Response\Http\Interceptor->___callPlugins('sendResponse',
Array, Array) #7
/home/tassosco/public_html/vendor/magento/framework/App/Http.php(185):
Magento\Framework\App\Response\Http\Interceptor->sendResponse() #8
/home/tassosco/public_html/vendor/magento/framework/App/Http.php(156):
Magento\Framework\App\Http->handleDeveloperMode(Object(Magento\Framework\App\Bootstrap),
Object(Exception)) #9
/home/tassosco/public_html/vendor/magento/framework/App/Bootstrap.php(263):
Magento\Framework\App\Http->catchException(Object(Magento\Framework\App\Bootstrap),
Object(Exception)) #10 /home/tassosco/public_html/index.php(39):
Magento\Framework\App\Bootstrap->run(Object(Magento\Framework\App\Http))

11 {main}

please help me?