Hello, Naborhi,
1, 2/ WooCommerce > Settings > Products > Inventory > Out of stock visibility > Hide out of stock items from the catalog – try this option.
3/ To enable the Classic Widgets Panel, please navigate to Theme Options > General and set the Enable Classic Widgets Panel option to On. Then, go to Appearance > Widgets – https://prnt.sc/uNqCYwjYtkoz
Here is screenshot of Theme options > WooCommerce > Shop > Shop page Filters: https://prnt.sc/9OGclUtI4uxS
4/ Custom CSS code can be used to achieve the desired result. Please provide us with the URL of your Shop page via the Private Content area here, and we will provide you with the code.
Kind Regards,
8theme team