Learn Turkish: Sunumumuz kısa. - Our presentation is short.

The root word is sunum (presentation). To say "our", we add the 1st person plural possessive suffix. Because sunum ends in a consonant, the suffix takes the form -(I)mIz. So, sunum + -umuz = sunumumuz.

Why is the suffix exactly -umuz here, instead of -ımız or -imiz?

It follows 4-way vowel harmony. We look at the last vowel in the root word sunum, which is u. According to the rules, if the last vowel is o or u, the suffix uses the vowel u. That is why the suffix becomes -umuz.

Could I say Bizim sunumumuz kısa instead?

Yes, you could! Bizim is the pronoun for "our". However, because the suffix -umuz already clearly shows that the presentation belongs to "us", adding bizim is optional. Turkish speakers usually leave it out unless they want to emphasize that it is our presentation, not someone else's.

Where is the word for "is" in this sentence?