I bet they are already on this website and have mastered English haha If they have the ability to come on this planet I'm sure they have studied our languages already.

I think this kind of depends on what your own personal vision of what aliens are. For all we know the concept of auditory language may be unknown to them. For instance, most insects in nature communicate through smell (For instance, ants communicate highly effectively based on smell, bee's when scared release a toxin that causes them all to become scared, which is why when you scare one bee you may end with the entire hive attacking you). Some even communicate through lite, such as the firefly. Perhaps the most clever of your options may have been math. Math is generally a ground up concept that does not contradict itself, and therefore could theoretically be used to communicate across a language barrier. We kind of assume any other kind of intelligent life form will be very similar to ourselves, which is a dangerous assumption. Intelligent life could very well have evolved aquatically, in which case communication would be very difficult. Also, is the concept of disease. We don't know what kind of pathogens an alien species that's never been on Earth may contain. What may be a common cold to them, could wipe out half the planet here. Communication isn't always a good thing. Any kind of "friendly" race would likely not hop onto our planet and say hello. As a society, they would probably realize the mess that could cause and the dangers inherent. First communication would likely take place through radio signals or photonics from a distance.