easy ways to stay fit?

i used to do tkd, gymnastics, figure skating, and swimming as a kid. as a teen, i do cheerleading but thats about it, and its more like a dance team than anything (no stunting here). i have a butt load of health issues, both physical and mental, and most of it is hereditary. i was recently told at a blood test that if i dont start exercising more, my life span might be reaaaally short. my dad (where my heart issues come from) has been a vigorous health nut since before j was born, and is even a black belt. he walks everywhere and is probably going to outlive me 😭😭. so i want to get serious about my exercise regimen for health reasons (and because a flat tummy wouldnt be bad 😜).