Prestashop product prices can't be changed and need SEO assistance.

General information for the website: Printers and cartridges Kind of development: Customization of existing blog Description of every page/module: Prestashop - The product price changes don't save. There is an error message at the top of the page. The website also needs some on page SEO consultation, and other tips and recommandations. Description of requirements/features: Notice: Undefined index: id_product in /var/www/vhosts/mywebsite/public_html/store/classes/Product.php on line 2438 Specific technologies required: Prestashop, SEO experience Extra notes: