What is the fastest way to learn a new language as an adult?

Consistency beats intensity. Combine a short daily app session for vocabulary with at least one real conversation a week, even if it is awkward at first. Listening to podcasts or shows in the language during your commute adds a lot.

Learn the 1,000 most common words first, they cover most everyday speech. Then start speaking as early as you can instead of waiting until you feel ready.

A tutor for 30 minutes twice a week kept me motivated more than any app.