Learn Italian: Avrò un progetto importante in primavera. - I will have an important project in spring.

The verb avere (to have) has an irregular stem in the future tense. Instead of just dropping the final -e to make "aver-", it drops the middle -e- completely, becoming avr-. Then you add the regular first-person future ending -ò.

Why does avrò have an accent mark on the last letter?

In the future tense, the first-person singular ending (-ò) and the third-person singular ending (-à) always have a written accent. This reminds you to place the spoken stress firmly on that final vowel.

Is progetto masculine, and if so, why does importante end in -e?

Yes, progetto is a masculine noun. The adjective importante ends in -e because it belongs to a specific group of adjectives that use the -e ending for both masculine and feminine singular nouns. It only changes to -i when plural.

Why do we use the preposition in before primavera?