The key is to rebuild slowly and deliberately, not to try to make up for lost time. Treat the first month as a gentle re-entry where the goal is consistency, not intensity. You can regain your C1 level, but only if you cap your study time and measure success differently.
Start with a 4 week re-entry phase. Keep it to 20 to 30 minutes a day of mostly input and light, low pressure use. Listen to a German podcast while walking, read a page or two of something you genuinely enjoy, and send one short voice message to a patient conversation partner. Do not open grammar books yet. Accept that your speaking feels weaker. That is temporary. Because you already reached C1, the neural pathways are still there. They just need reactivation, not punishment.
After the re-entry phase, move to a structured but small routine. Fifty minutes a day is enough, and choose a fixed time so it becomes automatic. Split it roughly into 15 minutes of listening or reading, 15 minutes of active speaking or writing, 15 minutes of targeted grammar or vocabulary review, and 5 minutes to log what you did. Do not do more. If you feel motivated and want extra, spend the extra time on fun input like a series or a music playlist, not on another workbook.
The biggest risk is comparing yourself to your pre burnout level. Your teacher said you can do it, and that was honest. But returning to C1 is not a linear race. You will have good days and bad days. Plan two rest days per week, and use a rule called never miss twice. If you miss one day, that is fine. If you miss two days, adjust the next day to just five minutes of listening. This prevents the all or nothing cycle that caused burnout.
Be explicit about tradeoffs. Rebuilding C1 will probably take longer than you want. If you join an intensive course immediately, you may feel strong for two weeks and then crash. Instead, for the first two months, avoid heavy classes or expensive tutoring. Use a self study routine, one conversation partner, and one weakness you identified from Goethe feedback. Choose one grammar topic, one type of writing, or one speaking skill. Master that before moving on.
Concrete next steps: pick one podcast, one book or article source, and one weekly conversation partner. Keep a simple log of what you did, not a grade. After four weeks, ask your teacher or a trusted speaker for a short informal assessment. Then adjust based on their feedback. This way you build evidence that you are returning, without forcing a high stakes goal too early.