Sometimes, we must perform a difficult project.

It is raining all day but it is warm. Before long, it will be spring. Five years ago, I performed a difficult project. That is to construct government financial information system. Sometimes, we must perform a difficult project in spite of knowing it is very difficult. We must do it to keep our promise. We must do it to perform our responsibility. In that case, we must satisfy our customer even if we don't know them well.

It is raining all day but it is warm.
>>> It's been raining all day but it's warm.

Before long, it will be spring.
>>> It won't be too long and it's Spring again.

Five years ago, I performed a difficult project.
>>> Five years ago, I had a difficult project.

That is to construct government financial information system.
>>> That is to construct government financial information system.--(correct)

Sometimes, we must perform a difficult project
>>> Sometimes, we have to face difficult project.

in spite of knowing it is very difficult.
>>> In spite all the knowledge I got, I find it hard to do.

We must do it to keep our promise.
>>> We have to do it because we have to meet the deadline.

We must do it to perform our responsibility.
>>> We have to because it is our job.

In that case, we must satisfy our customer
>>> In this case, we have to satisfy our clients.

even if we don't know them well.
>>> Even if we don't know them well.