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I've read 'efficienct' and 'effective' on W-M and other good sites.

I am trying to make some sentences, please comment.
As having been a project manager for 5 years, I think the people I'm working with now are very efficient, they can always accomplish their heavy tasks ahead of time, and hardly delay my project schedule. In addition, their proficiency has made our product more effective.

Pastel
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CORRECTED SENTENCES: 'Having been a project manager for five years, I think that the people I am working with now are very efficient: they always accomplish their heavy tasks ahead of time, and seldom delay my project schedule. In addition, their proficiency has made our product more effective.'

Written grammar and sentence structure has been corrected. If this is a formal report, do not use contractions, and write out small numbers in letters.

However, there are also some logical or word-choice problems:

(1) If the workers always accomplish their tasks on time, how could they ever delay the project schedule?

(2) Products, if effective, cannot be made so by the worker, but only by the designer.

'Efficient' refers to productivity without waste.
'Effective' refers to accomplishing an objective.