I created a few zones in the garden.
The first zone is situated in front of the house, and I suggest some junipers (Juniperus squamata) along with roses (Rosa sp.) to grow there.
The following zones are located behind the house. They are separated from each other by a winding path (gravel or stone), which will visually widen a narrow space of the garden. The path will be broken in two points so it is possible to walk from one zone to another. The distinction of the zones will make the garden space more attractive.
The recreational zone is situated near the terrace, and here the landlords together with their family and friends can spend their time meeting, eating, drinking, etc. Apart from a couple of furniture elements (eg. chairs, armchairs, table) you can arrange here a few big pots with Astilbe sp. (eg. Astilbe arendsii) and Echinacea sp. Near the tterrace, on a lawn, there is a place for a small paddling pool, for a summertime.
Another two zones are for relaxation purposes.
I suggest to plant some species along the path to colour it a bit – eg. 60-100 cm high grasses (Fescue Festuca cinerea, panic grass Panicum virgatum), Japanese spirea (Spiraea japonica) shrubs and a few perennial species – eg. peach-leaved bellflower (Campanula persicifolia) or triangle pink (Dianthus deltoides).
The shrubs growing at the end of the garden (the same species as in the front zone – junipers and roses) are an extension of the path. The shrubs refer to the plants growing in front of the house and compose a nice closing of the relaxation zone.
The plant species chosen for this garden create a mild, green and violet colour compositions, without excess of hues (we have to be very careful while picking colours for such a small space).