Everyone’s zone 5 is different and by definition you can’t spend much more than 5-12min in zone 5, so if your runs are longer than this, then the answer is no, you don’t. If you’re a beginner, try to run at a pace that seems easy and you’re able to breathe normally , don’t think about zones too much. After a couple of months, you can do some testing and set your zones right 😃 If you’re interested in how to do it, i’m always happy to help

in 1 month you can build some aerobic capacity, but for a better recording I suggest to get an hearth rate monitor band, because watches are not much accurate. The hardest part is to be patient in the beginning and keep the heart rate in zone 2/3 even if this means alternate run/walk. But in some weeks you will see the results and (most important) more chances to stay injury free

You probably aren’t in Zone 5, especially if you used a formula instead of testing your max HR.