5. Misuse of "Have" wrong: I haven't a pen. correct: I don't have a pen. This mistake comes either from the correct idiomatic phrase "I haven't got a pen," or some teacher in a Spanish school got hold of a 50- year-old English grammar book in which "I haven't the time," and such things were taught. In any case, it is not often used now. Better to use the structure of the present tense which requires doesn't/don't in a negative sentence. Have is not an auxiliary in the present tense. Have and has are auxiliaries in the present perfect only.
6. "People" as a singular noun wrong: The people is very angry at the tax increase. correct: People are very angry at the tax increase. Students translate "people" which is plural in English (people=persons) as " gente " which is singular in Spanish. The fact that "people" is an irregular plural (without an "s") doesn't help matters.