My battery health is 78% What can I do to Increase it's health

If it's below 80% and within your warranty period they will replace the battery for free. Until the end of the year Apple will replace it for $29. After that the price will go up depending on the device you have.

I was going to suggest you take it to a healer but they will just rip you off.

The only way you can increase the health of your battery is to pay to have Apple replace it.

And if they have an iPhone 5s or earlier it will be $79.