What language should you pray in, if not Hebrew?

Question

If someone were multilingual but could not speak Hebrew, what language would it be preferable for them to pray in? For example, someone who can speak English, Spanish, and Korean only. This is assuming they have access to Siddurim with accurate translations of each language.

Answer 1

Peninei Halakha answers your question here.

The mitzvah of prayer is ideally performed in Hebrew, for that is the language in which Anshei Knesset HaGedolah composed the wording of prayer, and it is the Holy Tongue which was used to create the world. However, b’dieved, a person who does not understand Hebrew may fulfill his obligation in other languages (Sotah 32a; Shulchan Aruch 62:2) [...]

In practice, a person who does not understand Hebrew is permitted to choose the language in which he wants to pray. Although the advantage of praying in a language that he understands is that he can concentrate on the words, on the other hand, one who prays in Hebrew has the benefit of praying in the Holy Tongue, for every Hebrew letter is directed towards the rectification of all the spiritual worlds.

The mitzvah of reciting Shema, in principle, may also be fulfilled with a translation. However, some doubt was raised regarding the accuracy of the translation of a number of words. Therefore, today, in the opinion of some eminent Acharonim (later Torah authorities), one cannot fulfill his obligation of reciting Shema by saying a translation of the words (Mishnah Berurah 62:3; further in this book 15:9).

So you can choose and should pick the language you feel most comfortable in, ideally one where you can pick a high-quality translation. In parallel, you would be well advised to gradually learn to say the prayers in Hebrew, something that can be mastered by most over a few months of regular practice. The easiest is to take on one paragraph at a time and move to the next once you feel comfortable with the last.

For further references, see here and here.