Ask an arborist

It's a bit pointless trying to change the soil you plant a tree into. A bit of amelioration may be useful to give a tree a start and help it's root system adapt, although it can also be counter productive as it helps the competing weeds just as much. But in the long term a big tree needs a big rooting area, and it would take some serious work to change all that soil. You really need to plant plants that like the environment you have available. If you're on waterlogged clay, don't try to plant trees that like a free draining sand. The fact that you've already had two fail is a big clue. Try something else.