It really depends not only on the language you're learning, but your native language, where you're living, the purposes you're learning the language for, and your own confidence and standards for your language learning. There is no "easiest language to learn" at all, but you will learn a lot easier and quicker if you're learning a language closely related to your own. For instance, an English native speaker will be able to learn Scots or Dutch much "easier", in general, than if they were trying to learn Tagalog or Xhosa. You will also inevitably learn more quickly if you're immersed fully in the language, using it constantly from day to day. However, that will usually happen if you're living in a country where that language is the primary language, and in that setting your personal standards for the language will probably rise. If you're only trying to speak the language as a second language at home or something, you probably will feel confident enough to do that more quickly than if you're trying to interact with native speakers in their own country. I think most of all though it's important not to put too much emphasis on the end goal of "fluency", and rather to focus on each little goal on the way, like being able to hold a quick conversation, then being able to hold a conversation with a native speaker, being able to talk about technical topics and politics etc.