What is the interpretation of the succession of illnesses, accidents, thefts, and lack of success at work? Is this related to magic (sihr) or the evil eye (ayn)? Are there specific Quranic verses for such matters?

These calamities are a trial from Allah to elevate ranks and expiate sins, or a punishment for what you have committed. One must be content with Allah's decree, while avoiding the causes of calamities. We advise maintaining obedience to Allah, especially the obligatory acts, and abandoning major sins; for calamities may be due to forbidden things in the home or committing immoralities. The cause may also be magic or envy, and its cure is through ruqyah (Islamic incantation).