Tomato puree is sour when you add it right away, you bake it. That way it becomes sweeter in flavor. You can check if it's done by smelling. You will smell the sweetness.
The addition of sugar is at the taste. It's very dependent on the sourness of the tomatoes. Sometimes it seems that tomatoes are much sour than other times (even canned ones). Flavor at taste is my advice here.
You can substitute the peeled tomatoes with fresh ones, while they are in season. Then they'll have an optimal flour and structure. In other seasons choose canned once, because they're always better in flavor.
Slice the onion and garlic fine.
Grab the frying pan and put a little olive oil in it. Put the pan on the stove on low heat.
Add the onion and tomato paste and bake for 3 minutes. Then add the garlic and cook for another 2 minutes.
Put the skillet on the stove on low heat. Stir with a spoon carefully for about 3 minutes.
Add the ground beef and bake the minced beef until brown and done.
Throw in the collected herbs, salt, and pepper. Add the tomato/onion mixture with it, the peeled tomatoes, and sieved tomatoes. Add sugar and top it with a bay leaf. Put the lid on the pan and let simmer for 30 minutes. Stir occasionally.
Preheat the oven to 430 degrees Fahrenheit (220 degrees Celsius).
Spoon ⅓ of bolognese sauce in the baking dish.
Cover with a layer of lasagne sheets.
Repeat this once more.
Spoon the last bolognese sauce on the lasagne sheets and sprinkle with grated cheese or sliced mozzarella (or a combination).