Error Messages on updating plugins

Here are the messages I have received:

Strict Standards: Non-static method Improved_Simpler_CSS::init() should not be called statically in /home1/profetb3/public_html/publicaffairsjobs/wp-content/plugins/imporved-simpler-css/improved-simpler-css.php on line 384

Strict Standards: call_user_func_array() expects parameter 1 to be a valid callback, non-static method Improved_Simpler_CSS::start() should not be called statically in /home1/profetb3/public_html/publicaffairsjobs/wp-includes/plugin.php on line 470

Strict Standards: call_user_func_array() expects parameter 1 to be a valid callback, non-static method Improved_Simpler_CSS::load_scripts() should not be called statically in /home1/profetb3/public_html/publicaffairsjobs/wp-includes/plugin.php on line 470

Strict Standards: call_user_func_array() expects parameter 1 to be a valid callback, non-static method Improved_Simpler_CSS::load_style() should not be called statically in /home1/profetb3/public_html/publicaffairsjobs/wp-includes/plugin.php on line 470

Strict Standards: call_user_func_array() expects parameter 1 to be a valid callback, non-static method Improved_Simpler_CSS::include_css() should not be called statically in /home1/profetb3/public_html/publicaffairsjobs/wp-includes/plugin.php on line 470

(Bold emphasis added)

Please advise what to do (Please note that I am NON-IT).

https://ww.wp.xz.cn/plugins/imporved-simpler-css/