I like to use fresh or frozen green beans. These give the best taste in my opinion and you can cook them the way you like them best.  Fresh and frozen beans take about 10-15 minutes, depending on how soft or firm you want them to be.   If you want to use fresh green beans, you can also blanch them briefly. So the great green color remains. And with fresh beans you have to do one more step, wash and cut them. You are now under time pressure. If you do not have a lot of time and still want to cook this delicious soup, then of course you can go back to canned green beans.  Please note that the beans are heated only for 2-3 minutes, as they are already cooked