Growing in back fill

Hello all. I am trying to grow in a location that was recently filled in via back fill. Perhaps not the best place to be doing this growing endeavor. We are doing cut flowers...they do okay if transplanted. When grown from seed, in particular, zinnia, they were stunted in growth. We tilled in compost this past season trying to add some organic material and then layered organic material on top. Recently I went in dog through the layered top of compost into the rolled layer and it was a wet gloopy mess. I showed my soil professor and he said it was really silty, small fine particles...not clay..but for non porous so water is not draining.  He suggest taking out the beds and putting in raised bed and gravel under them. I’m wondering though...do you think I can I prove the soil in this area or is it going to take ages? And if you do think I can improve the area what are your ideas? Should I till in a nicer mix of topsoil?

I think fixing it depends on a few things. Your planting zone, which direction the bed is facing and how much direct sunlight it gets. The one thing you can do immediately is make a hugelkultur. They are great as a hedge against drought but even better in overly wet soil. Once that’s complete take into account your zone and sunlight. Here in NC, zone 7b it’s cover crop season. I’m planting Austrian winter pea, winter rye, vetch, crimson clover and probably turnips. I have tested lots of cover crops and those work best here. If you are unsure I’d definitely recommend buying a deer plot mix for your zone.
If the area gets less that terrific sunlight plant some greens. Lettuce, kale, and turnips do very well in low light situations.