Akwai yiwuwar sabis ɗin ya dawo.

Yiwuwa means possibility or being possible. In this sentence it appears in a linking form, yiwuwar, which is roughly like possibility of... in English.

So:

• yiwuwa = possibility
• yiwuwar ... = possibility of ...

That final -r is part of the grammatical linking form, not a separate word.

sabis means service.
ɗin is a postposed determiner that often works a lot like English the. Depending on context, it can also feel a bit like that.

So sabis ɗin means the service.

In Hausa, the verb phrase agrees with the noun’s grammatical gender/class. Here sabis is being treated as a masculine singular noun, so the subject marker is ya.

That does not mean the service is biologically male. It is just grammatical agreement.

By itself, ya dawo can mean he/it returned or he/it has returned. But in this sentence, the larger expression Akwai yiwuwar... makes the meaning non-factual and uncertain.

So the whole sentence means something like:

• there is a possibility that it returns
• it may return
• it might come back

The idea of possibility comes from the whole construction, not from ya alone.

Because Hausa often does not need an extra word where English uses that.

English: There is a possibility that the service may return.
Hausa: Akwai yiwuwar sabis ɗin ya dawo.

So Hausa can go straight from yiwuwar to the clause that follows.

Because akwai yiwuwar already puts the event in an uncertain, non-established frame. In that kind of structure, Hausa commonly uses ya dawo.

This can confuse English speakers, because ya often looks like a past/perfective form when seen by itself. But here, because of the surrounding structure, the meaning is not simple past. It is understood as a possible future or possible eventual return.

Dawo means return, come back, or sometimes go back, depending on context.

In this sentence, the most natural English choices are usually:

• return
• come back

ɗ is a special Hausa consonant, different from plain d. It is an implosive d sound.

For a beginner, pronouncing it close to an ordinary English d is usually understood, but if you want more accurate Hausa pronunciation, it should sound distinct from plain d.