.modul-u--navbar {
    position: relative;
    border-top: $m-border-width--l solid $m-color--ul-yellow;

    &::after {
        position: absolute;
        bottom: $m-margin--s; // Magic number
        left: 0;
        right: 0;
        z-index: 0;
        content: '';
        height: 1px;
        background: $m-color--grey;
    }

    .m-navbar {
        position: relative;
        z-index: 1;

        // &__wrap {
        //     background: $m-color--white;
        // }

        .m-navbar-item.m--is-selected .modul-u--navbar__item {
            color: $modul-color--black-grey-dark;
        }
    }

    &__item {
        padding: 20px 0; //Magic Number
        font-weight: $m-font-weight--black;
        text-transform: uppercase;
        color: $modul-color--grey-dark;
        transition: color $m-transition-duration;

        &:hover,
        &:focus {
            color: $modul-color--grey-darker;
        }
    }
}

.modul-u--navbar {
    position: relative;
    border-top: $m-border-width--l solid $m-color--ul-yellow;

    &::after {
        position: absolute;
        bottom: $m-margin--s; // Magic number
        left: 0;
        right: 0;
        z-index: 0;
        content: '';
        height: 1px;
        background: $m-color--grey;
    }

    .m-navbar {
        position: relative;
        z-index: 1;

        // &__wrap {
        //     background: $m-color--white;
        // }

        .m-navbar-item.m--is-selected .modul-u--navbar__item {
            color: $modul-color--black-grey-dark;
        }
    }

    .m--is-skin-arrow {
        .m-navbar-item {
            .modul-u--navbar__item {
                padding: 20px 0; //Magic Number
                font-weight: $m-font-weight--black;
                text-transform: uppercase;
                color: $modul-color--grey-dark;

                &:hover,
                &:focus {
                    color: $modul-color--grey-darker;
                }
            }
        }
    }
}

Change following update to navbar css
Change following update to navbar css

