What is the easiest language to learn?
There’s no a correct answer and it actually depends on several factors such as your native language, your motivation and your “second language”.
Let’s say your native language is a Germanic one: probably another Germanic language would be easier for you to learn then a language belonging to a different “family”.
Also, in my opinion, if you are very motivated to learn a language it will significantly reduce the time you need to assimilate grammatical issues and memorise vocabulary.
To be already able to speak a second language can also be a key factor when learning a new one. For example, If you are an Arabic speaker who already studied Italian, learning another romance language like French or Spanish could require less time due to similar vocabulary and grammar.
For me, as an Italian native speaker, the easiest language to learn was (of course?) Spanish.
What is the easiest language to learn for you?