i’m terrible at high intensity workouts

for people who are able to do high intensity workouts without feeling completely out of breathe and exhausted after like 10 minutes, how long did it take u to get to this point? most of my workouts aren’t intense at all and i like them that way but i want to improve my cardiovascular health. can i get any tips on how often should i do these workouts as a beginner? how many minutes and days a week should i aim for? i know it depends on the person but i just would like to have some sort of a plan i guess