Migrating and Upgrading to Joomla! 4.x • Error when put error reporting to maximum

Code:

Deprecated: Joomla\Input\Input implements the Serializable interface, which is deprecated. Implement __serialize() and __unserialize() instead (or in addition, if support for old PHP versions is necessary) in /home3/mysite/public_html/i/libraries/vendor/joomla/input/src/Input.php on line 41Deprecated: Return type of Joomla\Input\Input::count() should either be compatible with Countable::count(): int, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in /home3/mysite/public_html/i/libraries/vendor/joomla/input/src/Input.php on line 170Deprecated: Joomla\CMS\Input\Input implements the Serializable interface, which is deprecated. Implement __serialize() and __unserialize() instead (or in addition, if support for old PHP versions is necessary) in /home3/mysite/public_html/i/libraries/src/Input/Input.php on line 31Warning: session_name(): Session name cannot be changed after headers have already been sent in /home3/mysite/public_html/i/libraries/joomla/session/handler/native.php on line 128Deprecated: Joomla\CMS\Input\Cookie implements the Serializable interface, which is deprecated. Implement __serialize() and __unserialize() instead (or in addition, if support for old PHP versions is necessary) in /home3/mysite/public_html/i/libraries/src/Input/Cookie.php on line 0Warning: session_cache_limiter(): Session cache limiter cannot be changed after headers have already been sent in /home3/mysite/public_html/i/libraries/joomla/session/handler/native.php on line 235Error: Failed to start application: Failed to start the session because headers have already been sent by "/home3/mysite/public_html/i/libraries/vendor/joomla/input/src/Input.php" at line 41.