I am _____ on the ambitious project of learning one new language every year.

The phrase 'embarking on' is a common idiomatic expression meaning to begin or start a new project, journey, or undertaking. It is typically followed by the preposition 'on'. 'Sailing on' doesn't fit naturally with projects. 'Adventuring' is not commonly paired with 'on' in this manner. 'Concurring' means to agree, which is contextually wrong. Hence, 'embarking' is the most appropriate choice.