It depends on the function of the verb 'have' in the sentence. 1. If 'have' is an auxiliary verb ('haber' in Spanish) you must use the form 'haven't'. eg I haven't seen that film. 2. If 'have' is the main verb in the sentence, and has the meaning of another verb (eg take), you must use the form 'don't have'. eg I don't have baths very often because I prefer to have showers. I don't have a big breakfast on weekdays because there isn't time. 3. If 'have' has the meaning of 'tener' in Spanish, then either form is possible. There is also a 3rd form : 'haven't got' A. I haven't time. B. I don't have time. C. I haven't got time. There is no difference in meaning between these forms. Form A is the least common. Form B can be either neutral or formal. It is used in both British and US English. Form C is more informal, and is used mainly in British English. I hope that helps.

They are two different tenses*. Negative past perfect: I have not gone = I haven't gone Negative present simple tense: I do not have a book = I don't have a book *in British English you may hear: "I haven't a book" meaning "I do not have a book". In American English that would be unusual.

All in the usage...practice and more practice

Same