If I understand your message correctly, you are looking for two things:
a) a current bank account as business account and
b) a bank loan
right?
A current account should be no problem with most banks unless you want it conected with a credit-line right from the beginning. If you want that you will need to show proof of more or less regular income from your occupation, otherwise chances are slim to get a credit-line right from the beginning. Banks might want to see balance sheets, current acounting and tax notes from the last years if available.
With regards to a loan, same problems apply. You might want to check with Commerzbank, some clients of mine told me that they are more friendly and open to freelancers and self-employed nowadays. Appart from that many freelancers/selfemployed seem to have made good experience with Raiffeisenbanks it would appear. These regional banks do have to the public assignment to support small and medium bussinesses... and sometimes they even do that.
One last thought: did you check your Schufa-records, i.e. that you are clean there? Sometimes things get reported to
Schufa that are not correct and might harm you in contacts with banks, therefore you better check that first.
Cheerio