Good Luck with your new home and garden.
Eventually you will hire, buy, or borrow a rotavator ( or someone who can use one ) You will rip up all that soil and mix compost or Brown Gold in through it and reseed it.
In the meantime, paint the wall white, and if you have pillars in the fencing, paint them too. This will really brighten up the place, those grey walls are so awful considering that we have so many grey days. All plants do well against a white wall, esp. helpful if it is a north facing wall.
The painting will break your heart, but will be worth it. Slap that paint on any way you can, good and thick. You will be told to 'Seal it first" I didn't bother and five years later the walls are still fine.
If you want, get a few cavity blocks and build a ' wall ', one block high where you want to plant stuff for this summer, paint them, get a bit of cheap timber board somewhere, paint it, and put it on top of your little wall. Back fill this with compost, and start planting. It is not ideal but is the cheapest, quickest way to start enjoying your garden.