Good job Deborah! Just a few corrections:

¿Por qué quiero aprender español? (Don't forget to use the question marks at the beginning and end of your questions)

*In Spanish, as in English, you have this kind of "freedom" to use or not the word "because" (Porque) after a question using "WHY", but it's more accurate and sounds more natural if you use it. 

**SOLO/SÓLO=  In Spanish there are two words that sound the same. The first one is an adjective and express loneliness, literally means ALONE (SOLO), e.g.: Me dio pena verla tan SOLA (I was sorry to see her so alone); while the second is an adverb and express that something is unique and it means ONLY (SÓLO), e.g.: ¡Estaba muy barato, SÓLO me costó 50 pesos! (It was very cheap, it ONLY cost me 50 pesos!) In your writing, you're trying to say that the parents ONLY speak in Spanish. Even when la RAE (Real Academia Española) accept that you can write SOLO en both cases, for you as a student it will be confused, and you should use the accent (la tilde) to clarify your idea.

Por qué quiero aprender español

En España la RAE (Real Academia de la Lengua Española) decidió que la palabra "solo" no debe llevar tilde:

http://www.rae.es/consultas/el-adverbio-solo-y-los-pronombres-demostrativos-sin-tilde

Aquí se puede ver esa misma norma, pero más simplificada: 

http://www.fundeu.es/recomendacion/solo-sin-tilde-193/