Version 1.6 cause theme to malfunction

I just updated to Version 1.6 and the theme got messed up. I get many errors like this:

( ! ) Strict standards: Declaration of New_Walker_Category::start_el() should be compatible with Walker_Category::start_el(&$output, $category, $depth = 0, $args = Array, $id = 0) in \themes\infopay\functions\theme-functions.php on line 212

( ! ) Strict standards: Declaration of DropDown_Nav_Menu::start_lvl() should be compatible with Walker_Nav_Menu::start_lvl(&$output, $depth = 0, $args = Array) in \wp-content\themes\infopay\functions\plugins\dropdown-menus.php on line 184

etc

https://ww.wp.xz.cn/plugins/recent-tweets-widget/