Berlin would have been “converted” to the vegan diet for some time, like many other European capitals: many restaurants were born offering only vegan menus, but for a few days in the (foreign) newspapers I have found the news of a German document, edited by the DGE, German Nutrition Society, where experts declare that the vegan diet would not give everything you need for a healthy diet, adding that it is difficult if not impossible for a vegan to get all the nutrients the body needs.
In reality, the document does NOT say that the vegan diet is bad or unbalanced , but it does explain that those who are on a vegan diet still have to worry about supplementing their usual diet with vitamin B12.
And that pregnant women, children and adolescents should not follow her,while there would be no problem for male or female adults in good health .

The advice of the experts is neither extreme nor catastrophic, so if you hear the news of German studies against the vegan diet do not listen to them, because you would feed useless alarmism. For those who want, here is the document of the German Nutrition Society, here .
For those who do not chew English, I will summarize some guidelines that can be really useful for those on a vegan diet and looking for non-synthetic alternatives for supplementing vitamin B12. 

HOW TO BECOME A HEALTHY VEGAN?
1) Relying on a nutritionist, in order to have a balanced diet plan from which it will then be easy to understand where to find all the nutrients the human body needs. Avoid DIY, even in the transition phase.
2) Pregnant women and children can follow a vegetarian diet more safely. 3) Vitamin B12 can also be integrated in a natural way, for example with: a) fermented vegetables (lactofermented), in particular lactofermented sauerkraut b) shiitake mushrooms c) spirulina algae 4) However these natural forms are of poor bioavailability for the Human Body. Therefore an integration is always and in any case recommended.

THE OUTLINE OF A BALANCED VEGAN DIET
1) 2 OR 3 DAILY PORTIONS OF POTATOES AND WHOLEMEAL CEREALS (BREAD UP TO 200 GR; Puffed CEREALS 50; POTATOES 250 GR; CEREALS IN CHICCO SUCH AS RICE 15O GR)
2) 400 GRAMS OF RAW VEGETABLES AND COOKED, AT LEAST, ON DAY
3) AT LEAST 300 GR OF FRUIT AND FROM 30 TO 60 GR OF DRIED FRUITS AND SEEDS, IN PARTICULAR ALMONDS AND SESAME (NO MORE)
4) FROM 50 TO 150 GR OF VEGETABLE PROTEINS, BETWEEN TOFU, SEITAN , ETC.
5) 2 MEALS PER WEEK OF AT LEAST LEGUMES
6) FROM 2-4 SPOONS OF OIL, BETWEEN: OLIVE, LINSEED, HEMP OIL
7) VITAMIN B12 ED INTEGRATIONS, OPEN AIR ACTIVITIES, TWO LITERS OF WATER ENRICHED WITH CALCIUM PER DAY.