Please help with my garden design

The picture has the side and top view of our garden. I’ve broken the garden into 2 parts A and B. I’m currently working on A.

General characteristics:
-Side of a hill
-Compacted soil
-Rocky layer underneath
-Hydrophobic soil (after a short but heavy rain only the top 5cm of the soil is wet, all the rest of the water flows down the hill)
-Filled with grass, flowers and weeds
-Summer droughts are expected
-Summer rains are usually 10-30 min long, but heavy and don’t happen too often (last few years we had about 3 rains in 3 months with temperatures above 30 celsius that’s 86 fahrenheit. Everything is usually like a wasteland in the summer)

B:
-elevation 11-12 degrees
-rows of grapes planted
-it’s slightly tilted to the left side, so water flows slightly to the left

A:
-elevation 2-4 degrees
-I dug a swale to catch the rain water flowing down from B (the dark brown part of the picture)
-I used the soil from the swale to level a part of the area for planting (the yellow part of the picture)
-I’m planning on digging it up more and fill it with 2 hugelkultur beds to help with water retention and to add some organic material

The planting area of 3.5x4m is quite large for a single bed so I’ve decided to cut it in half and make 2 beds. A top bed and a bottom bed. The top bed would be right next to the swale. So it would get good amounts of rain water during droughts. But the bottom bed wouldn’t get much of it. So I was thinking of digging a horizontal swale across the planting area between the top and the bottom beds. And redirecting some of the water from the original swale. I’m just not sure how to do it. I could use some pipes or dig another swale around the planting area. Maybe add some little dams. Or I could try to make the whole swale leveled so all the water can be distributed evenly between the top and bottom beds.

Any ideas would be helpful that would help with water retention thanks.