What are some resources for speeding up learning of advanced German mathematics-vocabulary?
I learned quite quickly by browsing through this book: https://www.springer.com/de/book/9783322943804
A formal approach would be to start with the internet documentation for common core-standards and curricula (Rahmenlehrpläne) as implemented in a particular city or state in Germany, e.g., Berlin. Chrome will automatically prompt you to translate the page I've linked to. Table 1 of that page organizes these standards by subject/grade-level. From there, you need only look for key terms and translate.
A quick reference approach would be to Google translate a particular term and to Wiki its translation in the target language, i.e. German, and then to repeat with neighboring words in the target article until the context becomes clear.
Above you confirmed that you are addressing graduate level mathematics. In this case, my recommendation is to get hold of one or two well-written textbooks on core topics. Here are some examples:
- Ben Schweizer: Partielle Differentialgleichungen
- Folkmar Bornemann: Numerische lineare Algebra
- Christian Hesse: Wahrscheinlichkeitstheorie.
In this way, you will pick up the vocabulary much faster than with any word lists or dictionaries, and you will get a realistic feeling for mathematical writing in German.