I'd cook the chicken whole in broth (with maybe some white wine) and the celery, tomatoes and bell pepper in it (and thyme, salt and pepper). The potatoes I'd cut in half, and roast in the oven together with the sliced onion, coated with a splash of cooking oil and salt. The bell pepper might actually be better in this too. To me, squash is more familiar as a racket sport, so I don't know what to do with it. Maybe dessert? Some sort of pie, with a butter-sugar-flour-oatmeal-cardamom crust served with vanilla ice cream or custard. The flour (or at least part of it) can be switched to ground almond.