Learn Romanian: Inginerii au un proiect. - The engineers have a project.

In Romanian, the first -i makes a masculine noun plural, and the second -i adds the meaning of the word the. The base word is inginer (engineer). You make it plural to get ingineri (engineers), and then add the second -i for the definite article to get inginerii (the engineers).

Is au the matching form of the verb to have for they?

Yes! The verb a avea (to have) is irregular. For they, which is ei for a group of male or mixed-gender engineers, the form is au (they have). This is different from the he or she form, which is are.

Why do we use un before proiect?

Proiect is a neuter noun. In Romanian, neuter nouns act like masculine nouns in the singular and feminine nouns in the plural. Because it is singular here, it takes the masculine word for a or an, which is un.