My Battery health is 79% should i replaced my battery now?

Once battery capacity goes below 80% other battery problems can occur, such as increased internal resistance, which can cause the phone to shut down if there is a sudden increase in battery load, and, in a few cases, the battery can expand and push the screen out, as well as other damage. Having Apple change the battery is quick and inexpensive→iPhone Battery Replacement - Official Apple Support

Yes. It is recommended to get a new battery when the battery health is 80% or less.

Open the Settings app, tap on Battery, then Battery Health.

As battery health gets lower, the ability for the battery to maintain a charge for a longer period of time. You will find that you will need to charge the battery more often.

How do I check battery level

Settings > Battery > Health

Go to settings, battery, battery health.

How do I check power level in my iPhone 5s

Follow the instructions posted by me, kb1951, and deggie.