Health Test App, It Returns a Score Based on the Answers Given
If you wish to keep your implementation scheme, I only have one large critique:

Names are important

Your naming scheme should allow a 3rd party to understand your code from a cursory glance. You have a lot of sneaky implementations tucked into your functions that aren't expressed in your naming convention.

All of your operations are stateful, which is technically ok but you use a lot of verbage that makes it sound like they're functional operations with actual return values. All of your functions act on stateful variables. Your naming convention should reflect this through the use of verb phrases, as opposed to nouns.

resetStorage: A good variable name. It is a verb that acts on localStorage

getStorage: Misleading. The traditional usage of the verb get is to retrieve a value or perform a computation (and return it). You are assigning this.healthScore. getStorage doesn't even have a return value. A more apt name would be something more like setHealthScoreFromLocalStorage.

toZero: What exactly is being set to zero? From the rest of your code (looking at resetStorage) I can infer that the value of 0 is the default value. It should be more along the lines of resetHealthScore or clearHealthScore.

returnMessage: It is updating this.message. So something more like updateHealthMessage?