Do you have any more pictures from other angles to help with the planning?
Also, once you've got your garden planned out, you should consider EasyTurf for the rest of the lawn - no maintenance or water hassle (saving you tons of money) - and we're very kid friendly. No dirt, no bugs, no grass stains on clothes AND EasyTurf looks and feels like the real thing!
Let me know what questions you have - and if you can, upload a few more photos so we can plan this garden out.
Cheers!
George
http://www.houzz.com/projects/82915/Backyard-Installations

Hey George, thank you very much for your comment. I just have started with the planning, but didn't think about artificial lawn. Sorry :( We would like to have some fruits (strawberries, apple tree, cherry and raspberries, for example, but also a playground for children surrounded or only a real grass. Attached are some pictures from different angles. Best, Sanida

Wow - first of all, I would definitely bring in a till to churn the earth over and get rid of the weeds. You need to get rid of the weeds and add nutrients to the soil.

You say you planted boxwood (it is very slow growing so don't expect a hedge for 10 years). Is this against the brown or the black fence? If it is against the black fence, you could plant near the fence a little inwards, the cherry and the apple tree (get a specimen that is quite large so you get more than one apple or cherry in the next year). Also plant them in spots that hide neighbouring views into your garden in the summer.

Raspberries like to grow as a weed and the hedge of raspberries under the trees and along the brown fence could work very nicely.

The rest of the ground should be flattened and planted with grass seed to give a large lawn. You can perhaps add a climbing frame or slide for them....

I agree that the weeds need to go before anything else. It looks like you may need to get a retaining wall to create a couple of levels in your yard. Or at least, someone with a small bobcat mover to level it to a nice even slope. I think you really need to do the prep work first before you can even start planting things. The rocks look like a hazard to children right as they are now.

Thank you all for your great suggestions!