Cannot access the plugin

I cannot access the plugin page. After activating the wp_debug mode i receive the following error message:

Fatal error: Uncaught TypeError: json_decode(): Argument #1 ($json) must be of type string, stdClass given in …wp-content/plugins/product-recommendation-quiz-for-ecommerce/admin/class-product-recommendation-quiz-for-ecommerce-admin.php:261 Stack trace: #0 …wp-content/plugins/product-recommendation-quiz-for-ecommerce/admin/class-product-recommendation-quiz-for-ecommerce-admin.php(261): json_decode() #1 …wp-content/plugins/product-recommendation-quiz-for-ecommerce/admin/class-product-recommendation-quiz-for-ecommerce-admin.php(343): Product_Recommendation_Quiz_For_Ecommerce_Admin->isJson() #2 …wp-includes/class-wp-hook.php(308): Product_Recommendation_Quiz_For_Ecommerce_Admin->prquiz_options() #3 …wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters() #4 …wp-includes/plugin.php(517): WP_Hook->do_action() #5 …wp-admin/admin.php(259): do_action() #6 {main} thrown in …wp-content/plugins/product-recommendation-quiz-for-ecommerce/admin/class-product-recommendation-quiz-for-ecommerce-admin.php on line 261

Can someone help here?