Practical Solution (proven):
• Use a reliable delivery address in Germany (friend/family) and clearly state it as "correspondence address" in the application.
• Create a simple power of attorney so that the person can open/scan letters and possibly make phone calls (otherwise, many authorities will not provide information).
• Always include case number + name + date of birth in the subject line (if case number is missing: "Case number: n/a").
• Don't ask "How long does Approbation take?", but rather: "Is my file complete / is anything missing?" – you're more likely to get an answer to that.
Additional Tip: Don't send originals, but certified copies + sworn translations (depending on the federal state). This protects you if you need documents again later abroad.