About how long does it take a normal and healthy male around the age of 18 to reach orgasm?

It depends. By masturbation, usually a few minutes unless you have had a recent ejaculation. It takes more time for men to have a second orgasm after an orgasm. From intercourse, it could take a few seconds (premature ejaculation) to not being able to have an ejaculation, especially if you have never had sex. First time sexual experiences don;t always work out very well. With practice, it usually gets better.