I could use some advice on how to add a web part zone to a page in Sharepoint 2013 on premise. I have not done any front-end customizations like this before. I have created a page based on the "Search results" layout. This layout has a left navigation zone where you can add web parts (for instance refinement panel) and a main zone where you can add web parts (usually search results). I would like to add a web part zone to the right, where there seem to be plenty of free space. How can I add that?
When I open the page in Sharepoint Designer and select "Edit page layout", I am only allowed to edit it in "advanced mode" and it seems like I am redirected to the master page "SearchResults.aspx". Also, it is not possible to insert "Web Part Zone" anywhere in the page...