Does it happen that people get rid of blackheads forever?

Not really. Wash face w gentle cleanser 2x/day. Use oil free products on face. No oily hair. No heavy foundations. Don't squeeze pimples. Avoid touching face (i.e., cradling chin in hands). Remove makeup before bed. Shower after strenuous exercise. Consider otc products (w salicylic acid or benzoyl peroxide). If > mild acne see dermatologist (discuss meds, comedone extractor, pore strips, etc.).
No. But your dermatologist can help you. The most effective therapy is tretinoin (retina).