That’s a subject in which you will have a large vary of opinions.
Some feed raw, some feed kibble. Just all kinda depends on your situation and what you are willing and capable of doing.
If you chose kibble, then there are some that are better than others. This is a good site that gives you an idea of good vs bad and the reasons why.
Dry Dog Food Reviews | Dog Food Advisor
A lot of us use to feed grain free kibble until recently it was put out to the public that grain free kibble is suspected of contributing to DCM- Dialated CardioMyopathy. I switched from Taste of the Wild to 4Health Performance, others switched to Holistic, FROMM, etc... it really depends on what you and your Doberman likes, some tend to have sensitive GI systems. Mine does not care, he will eat acorns and sticks if I let him.
He just wants to add a little fiber to his diet.
Search through the site for the different dog food posts. There is a lot of informative material that has been presented and discussed.