I finish too early during intercourse, do I need a longer foreplay?

Yes, it sounds like you need longer foreplay. If you define "sex" as intercourse only, your definition may be too narrow. You can enjoy oral, exploring with your hands, playing with her breasts, and much more and that can all be part of sex. Women definitely like it if you satisfy them too, and so you may like to go down on her before you have intercourse, and then the timing of your climax matters less to her. 

Having said that, things become less about how to have sex for a long time and more about medical issues if you always climax early, like in under a minute. Make an appointment if that applies to you, because it may be solvable medically.