Five questions. Your target and your deadline do most of the work; the last two decide the close calls. Nothing is sent anywhere — this runs entirely in your browser.
Your method
How much to trust this. Questions 1, 2 and 3 rest on something solid: your target, your time and how far the language is from ones you know really do determine what is reachable.
Questions 4 and 5 are my judgement, not research. Personality correlates with how people perform in a language, but no study says extroverts should pick a different method. I include them because the method you will actually still be doing in month seven beats the one that is theoretically optimal — and that is a claim I am willing to defend.