Hard crust and bottom

Hi friends, I am very new to bread baking. I started my own starter and baked a loaf with it. It was okay not very good not bad kinda loaf but did taste good. I let my dough rise in the refrigerator for arnd 13 hours and then directly put it in 500deg hot oven in the morning in a dutch oven for 20 mnts covered and 25 mnts uncovered. My loaf's crust and bottom was very hard but the center was soft and yummy. Any ideas to solve this problem? Thanks in advance.