When it comes to gardening, I am still learning too. I planted some radishes this year, and so far the greens are growing but they don't have much of the radish filling in yet. Might be related to the heat we have this year which I expect is also affecting your lettuce. Sounds like your potatoes are not getting proper drainage if they are sopping wet. Our eggplants are coming along fine, mostly greens at this stage, but we expect the fruit to follow soon.
I planted Seascape everbearing strawberries in a new raised hügelkultur bed this year, and they are already producing strawberries. So that has been a big success story for me. My local nursery only sells the everbearing strawberries because she said people have more success with that type of plant here where I live. She told me I might get as many as 3 pickings of strawberries even the first year. From what I understand, the June bearing strawberry plants take 1 year to establish themselves and start producing the second year.
I don't have running water where my main garden is located. My plants in the main garden are not doing very well, expect for my hügelkultur beds. In theory, the wood in the bottom of the hügelkultur beds is supposed to retain water and release it later when the plants need it. I think that is what I am seeing this hot, dry, year so far. My "normal" raised beds are too dry and I cannot keep up with the watering they require.
I built a couple new hügelkultur raised beds in my back yard where I have access to running water. I have been hitting those beds with some water every other day. The plants in my new beds, with adequate watering, are doing fantastic. If you compared the new beds in the back yard to the plants growing in my main garden without good watering, you would think one gardener knows what he is doing and the other is struggling. Well, I guess that's me and this dry, hot summer has driven home the notion that I need better watering in my main garden.