[RuntimeException] 
Could not start session because headers have already been sent. "/var/www/u0669621/matica.by/bitrix/modules/main/include/prolog.php":1. (0)
/var/www/u0669621/matica.by/bitrix/modules/main/lib/session/session.php:124
#0: Bitrix\Main\Session\Session->start()
	/var/www/u0669621/matica.by/bitrix/modules/main/lib/session/kernelsessionproxy.php:52
#1: Bitrix\Main\Session\KernelSessionProxy->start()
	/var/www/u0669621/matica.by/bitrix/modules/main/include.php:299
#2: require_once(string)
	/var/www/u0669621/matica.by/bitrix/modules/main/include/prolog_before.php:14
#3: require_once(string)
	/var/www/u0669621/matica.by/bitrix/modules/main/include/prolog.php:11
#4: require_once(string)
	/var/www/u0669621/matica.by/bitrix/header.php:1
#5: require(string)
	/var/www/u0669621/matica.by/help/payment/index.php:2