Hi, thank you for using health care magic. I can understand your concerns. For your first query there is no definite answer , erection usally last till ejaculation or up till loss of arousal/intimacy in between sexual activity due to some environmental issues. For premature ejaculation use start-stop technique or squeeze technique. This will help to give you more control over ejaculation. Medicines like sertraline, clomipramine, Peroxetine also help in reducing premature ejaculation. This medicine is used for treating depression , but in premature ejaculation it also helps. Consult psychiatrist if you feel need for this medicine. For the third issue , sexual desire play a part. Many young male have second erection very easily. Use different position , role play, fantasy during second sexual activity which can increase desire in your part. Alternatively ask your partner to become more active which can help you get erection faster. As the desire goes down the second erection takes time. If you find it more troublesome and feel that this is something more , then I would suggest serum testosterone level testing. Hope this will help you. Regards.