Method
Ojalá is a dictionary of bridges: from the words Spanish took from Arabic to the Arabic spoken today.
Loanwords, not relatives
Spanish is a Romance language and Arabic a Semitic one: they are not family. These words are borrowings, most of them from the Andalusi Arabic spoken in the Iberian Peninsula between 711 and 1492. Sometimes Arabic was only the bridge: azúcar comes from Persian, and before that from Sanskrit.
Degrees of certainty
Certain: the standard etymology in the RAE's Diccionario de la lengua española and in Corriente. Probable: the majority view, with reservations. Disputed: specialists disagree, and the note says why.
How we write Arabic
In Arabic script with all its vowel marks (harakat), because learners need them. In Latin letters, a simple, consistent system: ā ī ū for long vowels, ḥ ṣ ḍ ṭ ẓ for the emphatics, ʿ for ʿayn, and the article written as it is pronounced (as-sukkar, ar-ruzz).
Three ways in
In Spanish, Ojalá teaches Arabic through words you already know. In Arabic, it flips: every Spanish word is also written in Arabic letters, so Arabic speakers can read it aloud. In English, you get both sides of the bridge.
Sources: Diccionario de la lengua española (RAE) and F. Corriente, Dictionary of Arabic and Allied Loanwords.