Este projeto demora mais tempo do que eu pensava.

In European Portuguese, demorar often means to take time or to last.

So:

• Este projeto demora... = This project takes...
• more literally: This project takes/delays...

It is a very common way to talk about how long something takes:

• A viagem demora duas horas. = The trip takes two hours.
• Isto demora muito tempo. = This takes a long time.

In your sentence, o projeto is the thing that takes time, so it is the subject of the verb.

Because Portuguese usually says more time explicitly in this kind of sentence.

• demora mais tempo = takes more time

In English, we often shorten this to takes longer, but Portuguese commonly keeps the noun:

• Demora mais tempo do que eu pensava.
• literally: It takes more time than I thought.

You may also hear:

• demora mais do que eu pensava = it takes longer than I thought

So both ideas exist, but mais tempo is very natural and clear.

Do que means than in comparisons.

Here it connects two ideas:

• mais tempo = more time
• do que eu pensava = than I thought

So:

• mais ... do que ... = more ... than ...

Examples:

• É mais difícil do que parece. = It’s more difficult than it seems.
• Gasta mais dinheiro do que devia. = He/She spends more money than he/she should.

With comparatives, do que is extremely common.

Pensava is the imperfect form of pensar. Here it means something like:

• I thought
• I was thinking
• I had thought / I used to think, depending on context

In this sentence, the imperfect sounds natural because it refers to your previous expectation or idea, not just one single completed moment of thinking.

So:

• do que eu pensava = than I thought / than I was expecting

If you said do que eu pensei, it would sound more like comparing with a specific moment when you thought something. That is possible in some contexts, but pensava is more natural for a general prior expectation.

Yes. Portuguese often drops subject pronouns when the verb ending already makes the subject clear.

So both are possible:

• do que eu pensava
• do que pensava

Since pensava can already suggest I/he/she was thinking depending on context, adding eu can make it clearer or slightly more emphatic.

In this sentence, eu is not wrong at all. It may simply help make the comparison more explicit:

• than I thought

In European Portuguese, este usually refers to something near the speaker or something the speaker is presenting as this.

• este = this
• esse = that (often nearer the listener or previously mentioned in a different way)

So:

• Este projeto = This project

For learners, the important thing is that este is the normal word for this. In real usage, demonstratives can vary a bit depending on context, but este projeto is completely standard.

Sometimes, depending on context, yes. But the most direct translation is project.

• projeto = project
• in some contexts, it can also mean plan, proposal, or draft

In your sentence, without more context, project is the safest and most natural translation.

Because the subject is singular:

• Este projeto = This project

So the verb must agree with it:

• Este projeto demora
• Estes projetos demoram

Compare:

• Este projeto demora mais tempo. = This project takes more time.
• Estes projetos demoram mais tempo. = These projects take more time.

Yes. A few natural Portuguese alternatives are:

• Este projeto está a demorar mais tempo do que eu pensava.
• Este projeto está a demorar mais do que eu pensava.

In European Portuguese, estar a + infinitive is the usual way to express an ongoing action:

• está a demorar = is taking / is taking longer

So your original sentence is correct and natural, but adding está a makes it feel more clearly ongoing.

Yes, in many contexts that works.

• Este projeto leva mais tempo do que eu pensava.
• Este projeto demora mais tempo do que eu pensava.

Both are understandable and natural. Roughly:

• levar tempo = to take time
• demorar = to take long / to last / to be slow

In everyday use, both can fit this sentence well.

The structure is:

• Este projeto = subject
• demora = verb
• mais tempo = object/complement expressing duration
• do que eu pensava = comparative clause

So:

• Este projeto / demora / mais tempo / do que eu pensava
• This project / takes / more time / than I thought

The word order is quite straightforward and close to English, except that Portuguese prefers more time where English often says longer.

A rough pronunciation guide for an English speaker is:

ESH-tuh pro-ZHEH-too dih-MOH-ruh mysh TEM-poo doo kuh ew pen-SAH-vuh

A few important European Portuguese points:

• este often sounds closer to esh-tuh
• projeto has a soft j like the s in measure
• unstressed vowels are often reduced, especially in European Portuguese
• do que is usually said quite quickly together

If you want, a very rough connected version would be:

Esh-t’pro-zheh-tu dih-mohr’ mysh temp’ du-ke eu pen-sah-v’

That rougher version is closer to natural fast speech, though less helpful for beginners.