

Roughly translated it means “not true” and can be used as that. But most often it is used as a filler/comfirming word like the English “right” both in the middle and in the end of sentences, and can also be shortened to just “sant”, “true”. So combined with the typically Nordic inward breathing “jah” you have half of a normal Norwegian conversation right there.
For a better ageing experience, you should start to regularly work out before you get older than your shoe size.