Kadiri unavyopiga mswaki kwa upole, ndivyo ufizi wako unavyobaki salama na hutahitaji kutema mate mengi.

This is a very common Swahili pattern for showing a proportional relationship.

It means something like:

• the more ..., the more ...
• as ..., so ...

So Kadiri unavyopiga mswaki kwa upole, ndivyo ufizi wako unavyobaki salama means:

• The more gently you brush your teeth, the more your gums stay safe
• or As you brush more gently, your gums stay safer

Kadiri introduces the degree or extent, and ndivyo introduces the matching result.

Because after kadiri, Swahili usually uses a relative-style form with -vyo- to mean how / the way that / as.

So unavyopiga can be broken down like this:

• u- = you, singular
• -na- = present
• -vyo- = relative/adverbial marker meaning how / in the way that
• -piga = hit / do / strike

In this expression, unavyopiga means roughly how you brush or the way you brush.

If you said just unapiga, that would simply mean you brush / you are brushing, but it would not fit the kadiri ... ndivyo ... structure as naturally.

Yes. Kupiga mswaki is a very common expression meaning to brush one’s teeth.

Even though -piga often literally means hit or strike, in many expressions it has a broader idiomatic meaning. So you should learn kupiga mswaki as a set phrase.

Also, mswaki can refer to a toothbrush, so the whole phrase is understood as brush the teeth even though meno is not explicitly mentioned here.

Because Swahili often expresses adverbs with kwa + noun rather than with a separate adverb form like English.

Here:

• kwa = with / in
• upole = gentleness

So kwa upole literally means with gentleness, but in natural English it is simply gently.

This pattern is very common in Swahili:

• kwa haraka = quickly
• kwa makini = carefully
• kwa nguvu = forcefully / strongly
• kwa upole = gently

Not this time.

In unavyobaki, the u- is not the you prefix. It is the subject agreement for ufizi.

So:

• unavyopiga → u- = you
• ufizi wako unavyobaki → u- = agreement with ufizi

That can be confusing because both are spelled the same.

So ufizi wako unavyobaki salama means how your gums remain safe, and the verb agrees with ufizi, not with you.

Because ufizi is often used as a collective noun, referring to the gums as a whole.

So even though English normally says gums, Swahili can use singular ufizi to refer to gum tissue in general.

You may also encounter fizi, but ufizi is very natural when talking about gums as one whole area of the mouth.

So:

• ufizi wako = your gums
• literally closer to your gum tissue

Because possessives in Swahili must agree with the noun class of the noun they describe.

Ufizi belongs to a noun class that takes the possessive agreement wa-, so:

• ufizi wako = your gums

This is why it is wako, not some other possessive form.

For comparison:

• meno yako = your teeth
• mkono wako = your hand
• kitabu chako = your book

The ending -ako means your, but the beginning changes to match the noun class.

Because salama is generally invariable in this kind of use.

It means safe, secure, or unharmed, and it often stays the same regardless of noun class.

So:

• mtoto salama
• watoto salama
• ufizi salama

This is normal. Not every descriptive word in Swahili changes form the way some adjectives do.

Hutahitaji means you will not need or you won’t have to.

It breaks down like this:

• hu- = negative subject prefix for you
• -ta- = future
• -hitaji = need

So:

• utahitaji = you will need
• hutahitaji = you will not need

In this sentence, it gives the result of brushing gently: you won’t need to spit a lot.

Literally, it means to spit a lot of saliva.

Parts:

• kutema = to spit
• mate = saliva / spit
• mengi = much / many, agreeing with mate

In natural English, you would usually say:

• to spit a lot
• to spit out a lot of saliva

So the Swahili is a bit more explicit than English.

You would change the you forms from singular to plural.

A natural plural version would be:

Kadiri mnavyopiga mswaki kwa upole, ndivyo ufizi wenu unavyobaki salama na hamtahitaji kutema mate mengi.

Main changes:

• unavyopiga → mnavyopiga = you all brush
• wako → wenu = your, plural
• hutahitaji → hamtahitaji = you all will not need

So the original sentence is addressed to one person, while this version is addressed to several people.