Yes, it's entirely normal in Germany to just walk in and consult a pharmacist about minor problems. They're generally quite friendly and not too busy, even in the middle of Berlin.
This used to be common in the US as well, but no longer. This is something that seems to have disappeared as the larger chain stores have take over the field.
When I was in the US, I had no issues with consulting with pharmacists at the Fred Meyer's Pharmacy nor at Walgreen's. No one encouraged me to not have a consultation, and they were very professional.
Even at chain stores in the US, one of the people behind the counter is a pharmacist who went to grad school for five years studying this stuff. (The person actually giving you your medication may only be a pharmacy tech, but they have to have a pharmacist behind the counter whenever they're open.)
Yes. The pharmacist almost certainly knows much more about drugs in general than a doctor does. The doctor is familiar with the drugs he prescribes, sure, but may not be at all familiar with the drugs that your other doctor prescribed. That is, your dermatologist knows all about dermatology drugs, but may not know much about your blood pressure or antidepressant medicine (in particular, that one of those drugs has a bad interaction with the dermatology medicine he's prescribing).
That's also why it's important to always go to the same pharmacy if you can. If you switch to a new one, make sure to switch all your prescriptions at the same time.
