Portfolio item – 1/2 + 1/2 layout

Hello,

I would like to split my portfolie item pages into 1/2 + 1/2 like it is possible in “Edit Page” page (Page edit.png).

Please see also “Actual state.png” – where is shown how my portfolio item page looks now and “Desired state.png” – where is sketchet how I would like to look like.

Could you advise me a way how to do it?

Thank you