#entrainements_acceuil {
    background: linear-gradient(to bottom left, rgba(219, 33, 34, 0), rgba(187, 0, 45, 0.75)),
    url('/assets/images/Entrainement_Kumite_Senior.jpg') no-repeat center center/cover;
}

#entrainements_acceuil .conteneur {
    width: 100%;
}