How to create a rooftop garden? 20,000 yuan gives a 20-year-old 5th-floor old house a new look

It's a very old house, only 5 floors, and I live on the top floor. Because of cost factors, the house was not designed with a turret, which means the stairs only go up to the 5th floor and do not go up to the roof.
The renovation cost about 20,000 in total. Considering the roof's load-bearing capacity, I did not fill too deep soil, nor did I add too many decorations. Of course, the bigger reason is that there was not enough money in my pocket.
This little ad is a bit scary
Back when the house was being decorated, I once wanted to renovate it a little so it would be convenient to go up to the roof, but in the end I gave up because it was too difficult.
Later, my daughter was born, so the idea of taking my daughter to the rooftop to sunbathe became more and more obvious.
The roof's original appearance. The protruding platform is a vent.
Looking across, two of the opposite residents had also gone up to the roof. One planted Sedum lineare on the roof for heat insulation, and the other made a water pool and a vegetable plot. But none of them modified the stairwell; they all climbed onto the roof through the reserved opening in that stairwell.
The lush Sedum lineare across the way
So I began my rooftop garden renovation project. To go up to the roof, the first step was to modify the stairwell. To make a steel-structured staircase, the hardest part was opening up the original roof and removing 4 hollow-core slabs, then building the wall and laying tiles. This project was very large and even more difficult. I also had to worry about objections from the neighbors next door and downstairs. So I first talked it over with the neighbors. Fortunately, our relationships were usually handled pretty well, and there were not too many opposing voices. I reckon everyone wanted to object, but for the sake of face they did not say much.
Let's first look at the picture of my stairwell
After the stairwell was done, going up to the roof became convenient, so I started the rooftop garden construction. I planned a movable panel house for storing odds and ends, built a water pool, and in addition divided off several plots of vegetable soil, made railings, welded a grape trellis.........
Water lilies and the pool, growing beautifully
This house does not look like much, but its quality is quite good. For more than ten years it has never leaked. In fact, spreading soil on the roof is better for waterproofing, because the roof's rigid waterproof layer will not crack due to thermal expansion and contraction, and the lifespan of the bitumen mastic is also longer.