Are there any errors in the text?

It's usually best to avoid starting sentences with Because.

Stylistically I wouldn't repeat complaints in the same sentence.

They dealt promptly with my complaints, the supervisor came to my house on the same day to address them.

Thanks.

The renovation work would not have been so efficiently carried out without the support of the public relations officers. They acted promptly on my complaints. The supervisor came to my house on the same day to attend to my complaints. This had been my observation throughout the period the workers did renovations to my apartment.

The last sentence does not seem to relate to the rest of the paragraph. Maybe that's because I don't know the context.

I like Jewels sentence better, and Ive tightnd it up a bit more.

The renovation work to my apartment would not have been efficiently completed without the support of the(company's) public relations officers. They acted promptly on my complaint, as witnessed by their supervisor who came to my house on the very same day I called .



You dont really need that last sentence since the entire paragraph is a demonstration of your "observations"