Bu altyapı projesi tamamlanınca, şehirde taşımacılık daha verimli olacak.

Projesi means its project or the project of ... and here it is part of a noun phrase:

• altyapı projesi = infrastructure project

In Turkish, when one noun modifies another noun like this, the second noun usually takes the 3rd person possessive ending:

• altyapı = infrastructure
• proje = project
• altyapı projesi = infrastructure project

This structure is extremely common in Turkish:

• okul binası = school building
• şehir merkezi = city center
• otobüs durağı = bus stop

So altyapı projesi is the natural Turkish way to say infrastructure project.

Bu means this.

So:

• bu altyapı projesi = this infrastructure project

It directly modifies the noun phrase that follows it.

Tamamlanınca means when it is completed or once it is completed.

It comes from:

• tamamlanmak = to be completed
• verb stem: tamamlan-
• -ınca / -ince / -unca / -ünce = when / once

So:

• tamamlanınca = when it is completed

This suffix attaches to verbs to create a time clause:

• gelince = when he/she comes
• bitince = when it ends / is finished
• görünce = when he/she sees

Here it links the first event to the second one:

• Bu altyapı projesi tamamlanınca = When this infrastructure project is completed

Because the verb is tamamlanmak, not tamamlamak.

• tamamlamak = to complete something
• tamamlanmak = to be completed

So:

• Projeyi tamamlamak = to complete the project
• Proje tamamlandı = the project was completed / the project is completed

In your sentence, the project is receiving the action, so Turkish uses the intransitive/passive-like form tamamlanmak.

Şehirde means in the city.

It is:

• şehir = city
• -de / -da = in / at

So:

• şehirde taşımacılık = transportation in the city

Compare:

• şehir = city
• şehirde = in the city
• şehri = the city (as object) / its city, depending on context

In this sentence, the idea is location, so the locative ending -de is used.

Taşımacılık means transportation, transport services, or the business/activity of transporting.

It comes from:

• taşımak = to carry, to transport
• taşımacı = transporter / carrier
• taşımacılık = transportation / transport work / transport sector

In this sentence, it refers to transportation in general within the city.

Daha verimli means more efficient.

• verimli = efficient, productive
• daha = more

So:

• verimli = efficient
• daha verimli = more efficient

This is the normal way Turkish forms the comparative:

• daha iyi = better
• daha hızlı = faster
• daha ucuz = cheaper

There is no special comparative ending like English -er. Turkish usually uses daha.

Olacak means will be.

It comes from:

• olmak = to be, to become
• future ending -acak / -ecek

So:

• verimli olacak = will be efficient
• daha verimli olacak = will be more efficient

The sentence is talking about a future result after the project is completed, so the future tense is natural.

Sometimes yes, but the meaning shifts a little.

• olacak = will be; a clear future prediction
• olur = can be more general, habitual, or sometimes a less explicit future

In this sentence, olacak is the best choice because it clearly says that after completion, transportation will become more efficient.

So:

• ... daha verimli olacak = straightforward future result

Turkish often places the time clause first and the main verb at the end.

Structure here:

• Bu altyapı projesi tamamlanınca = when this infrastructure project is completed
• şehirde taşımacılık = transportation in the city
• daha verimli olacak = will be more efficient

A very natural Turkish pattern is:

[time/background information] + [subject/topic] + [other details] + [main verb]

So the sentence order is very typical for Turkish.

Yes. In the main clause, taşımacılık is the subject.

Main clause:

• şehirde taşımacılık daha verimli olacak

This literally breaks down as:

• şehirde = in the city
• taşımacılık = transportation
• daha verimli = more efficient
• olacak = will be

So the thing that will be more efficient is taşımacılık.

Yes, very often in natural English translation it can be understood as:

• when it is completed
• once it is completed
• after it is completed

The Turkish suffix -ınca/-ince often marks the point at which the next action or state happens. The exact English wording depends on context.

Here, all of these are possible translations:

• When this infrastructure project is completed, transportation in the city will be more efficient.
• Once this infrastructure project is completed, transportation in the city will be more efficient.

Yes, that is close to the structure of the Turkish, but in natural English is completed usually sounds better than gets completed here.

Turkish does not force exactly the same distinction English does between:

• is completed
• gets completed

So while gets completed is possible, the most natural English meaning is:

When this infrastructure project is completed, transportation in the city will be more efficient.