Felting a pitcher roof , guttering and change of soffits and fascia boards

Build 8m wide garden retaining wall, max 800cm high. Lay concrete base extension, 8m wide x 115cm depth x 100mm height. Supply all material and clean up afterwards. The domestic site is fully prepared. The retaining wall is to be built on existing concrete base.

I would like to build an extension using the garden of my home in Slough 6x3x3 mt