This is an irregular verb. It follows the conjugation pattern of the verb pedir.
PresentPresente
Mi hermana compite en natación cada verano.
My sister competes in swimming every summer.
PreteritePretérito indefinido
En marzo compitieron en el torneo nacional.
In March they competed in the national tournament.
FutureFuturo
El sábado competiremos contra el mejor equipo.
On Saturday we will compete against the best team.