Upvote:0
There is a great app I have found that is a Schengen calculator app. You can put in and lock days you have already been in the Schengen area, then go forward a put in proposed travel days. It's very useful. It tells you when you must leave by and when you can return as it takes in the rolling 180 day period.
Upvote:4
The Schengen rules are a rolling window. You can spend 90 days out of every 180 days outside the country of your long-stay visa. Today is May 14th, 2021, so visits before November 16th, 2020 do not matter any more. Tomorrow, the window will be November 17th to May 15th. The day after that, it will be November 18th to May 16th.
The visits in December and early March do count. The visit in November may or may not count, depending on when you left. Count the days (and remember that partial days count in full, and so do visits/transits in other Schengen member states outside Germany).
Between March 21th, 2021, and May 14th, 2021, you have used up 55 days.