My Answer: Baal HaSulam writes that Hebrew is the language of the Light and Aramaic is the language of the vessel of reception (the Kli). These two languages correspond to the front and back side, respectively. They are the main languages in Kabbalah because the geometrical shape of their letters portrays the connection between the Light and the desires (Kelim).
But these are just basic languages because they emerged in the very beginning of the division of Babylon and humanity’s separation from each other. The letters mark the properties of the corrected souls (the vessels, Kelim). The horizontal lines correspond to the spreading of the Light of Hassidim, and the vertical lines of the letters correspond to spreading of the Light of Hochma.
Other languages emerged from the ever-growing egoistic separation between people from the time of ancient Babylon, when egoism was revealed in flashes in the basic human civilization. These languages are not artificial, since people invented them from within their own nature. However, they arose far from the Source, from the breaking that happened in Babylon. That is why Kabbalists did not give us any explanations of the letters of these “secondary” languages, and did not describe which property and connection each letter portrays between the Light and the Kli.
In both Hebrew and Aramaic, each letter is a model, a symbol, and a recording of the connection between the Light and the Kli. It is a connection of the properties of Bina and Malchut: nine letters of ZAT of Bina, nine letters of Zeir Anpin, four letters of Malchut and the five final letters (Mantzepach), as well as the shape corresponding to their properties.
Therefore, a person studying the science of Kabbalah has to know the elements of the letters of the Hebrew alphabet. In fact, their geometrical shape conveys the spiritual properties of Malchut and the extent of its remoteness from Bina.
The letter itself is a recording of a spiritual state. A person should attain the properties of all the letters (meaning, the connections between the properties of reception – Malchut and bestowal – Bina) and “write them down” in his heart (his desire) in the correct order. He will then receive the whole text of the Torah, as it is written, “Record it in your heart!”