It is completely normal to have sexual desire, whether you are married or unmarried, as it is a natural part of human biology. There is no fixed normal duration for sexual intercourse, but on average, it may last a few minutes (often around 3-7 minutes of penetration), and satisfaction varies more with comfort and communication than time. Masturbation is generally safe and does not harm your health when done in moderation; it does not cause weakness, infertility, or long-term problems, and it also does not heat or cool the body in any medical sense, as these are common myths. However, if it becomes excessive or interferes with daily life, it is better to seek guidance. Overall, your concerns are normal, and maintaining a healthy lifestyle and balanced mindset is what matters most.