A little and often is the way to go with language learning. Duolingo offers a fun and effective way of brushing up your French bit by bit, up and including CEFR level B2. You can even select to have your own coach send you gentle reminders if you slip up some days... and then catch up on lost time. Great to see how you are really progressing. From Google App store: click here. From Apple App store: click here.