The Product Grid module displays a grid of all the products on the page. There are many customization options available there to make sure you can change the style of your product grid.
To change the number of columns for a mobile device in Product Grid, first, enter the page builder.
Step 1: Insert a product grid on the page by drag and drop operation or if the grid is already on the page, click on the little wrench icon to enter the product grid settings.
Step 2: Now look for the Columns options in the Structure submenu, in the Layout Tab.
Step 3: Click on the little Desktop logo beside the Text Feild (as shown in the image). This will change the responsive device to Tablet. Click on it again to change the responsive device to Mobile. You can also see the change live in the page editor.
Step 4: Now you can enter the value for the number of columns in the text field and it will reflect on the page builder in real-time.