"Do you serve breakfast?"
Translation:Est-ce que vous servez le petit déjeuner ?
Servir is an irregular verb. The tu form is sers. There are several -ir verbs conjugated in a similar way: dormir, partir, sortir, etc. With (the present indicative of) these verbs, the plural forms are like regular -er verbs, and the singular forms take off the final consonant of the stem and add s/s/t: