Elena: Many but not all Spanish words that start with “al” are originally Arabic. “Almuerzo” is not Arabic. It came from Latin, but “al” was added due to the influence of Arabic.
Imen: وسادة and مخدة are both correct in standard Arabic. مخدة is derived from خد (cheek) and specifically denotes a pillow that you sleep on (i.e. that you rest your cheek on).
To respond to the OP: Many words that relate to agriculture are either derived from Arabic or arrived to the West from other languages via Arabic. The reason is that Arabs revolutionized the agricultural industry and played a significant role in the development of mass cultivation, including coffee (qahwa), sugar (sukkar), lemon (laymoon), and orange (this word is derived from “naaranj”, which in Arabic refers to a bitter orange that used to be common and the Arabs introduced to the West through Andalusia. In English, this type of orange is called “Seville orange”, after the city in Andalusia).