If you are writting in Spanish you must use this letter ñ, because the mean changes. 

The correct form is Mi español es terrible.

Hola, mi nomber es Christina. Mis amigos me llaman "Cricket," como el insecto. When you are talking about your friends it is in plural, you must write 's' to the end.
Llevo Solo dos semestres de clases de español y tengo una D en la segunda clase. 

I don't know how long have you studied Spanish?and What does your phrase mean?

Sé que los números, y las letras. y los tacos. :) An finally your sentence don't have mean.

Your Spanish "No es tan terrible". Come on you can do it.

I hope help you and I need you because like you I learn English.

PS. Have you ever eaten 'tacos'? because they are so delicious.... mmm!!