Plz explain the handicap

Hello

As the subject says i would love some1 to explain in lehmans terms how the handicap system works.

I have only been playing golf since december and are unsure on alot of the rules.

I was told by a friend that your handicap lowers by 0.2 points every hole you score under your par and 0.1 added to your handicap for every hole over your par.

Today i shot a 99 on a par71 course including 3 pars, 6 bogeys, 6 double bogeys and 3 no-scores ( higher than double-bogey) yet my handicap which is set at 27 hasnt changed.

This seems odd to me as 4 the 8 rounds i have played my handicap has stayed the same.

Could it be because my partner and i play through a society and not by adding a round?

Plz help

Stuart