não deu certo otimizar os códigos.

o código inserido primeiro mostra a imagem normal, quando otimizado as imagens desaparece.

* elemento de destaque*/
/* o código comentado foi cpomrimido usando atalhos (shorthands)*/
.destaques__principal{
    background-image:url("../img/fortnite.jpg"); 
   /* background: center / cover no-repeat;
    grid-column: 1/4;
    grid-row: 1/3;
    /**/
    background-position: center;
    background-repeat: no-repeat;
    background-size: cover;
    grid-column-start: 1;
    grid-column-end: 4;
    grid-row-start: 1;
    grid-row-end: 3;

}
/*conteudo secundario*/
.destaques__secundario:nth-child(2){
    background-image:url("../img/pubg.jpg") center / no-repeat / cover;
    grid-column: 4/5;
    grid-row: 1/2;
    /*
    background-position: center;
    background-repeat: no-repeat;
    background-size: cover;
    grid-column-start: 4;
    grid-column-end: 5;
    grid-row-start: 1;
    grid-row-end: 2;
    */
}
/* codigos jaatimizados */
.destaques__secundario:nth-child(3){
    background-image:url("../img/slack.png") center / no-repeat / cover;
    grid-column: 4/5;
    grid-row: 2/3;
}
.destaques__secundario:nth-child(4){
    background-image:url("../img/whatsapp.png") center / no-repeat / cover;
    grid-column: 4/5;
    grid-row: 3/4;
}
.destaques__secundario:nth-child(5){
    background-image:url("../img/cs-go.jpg") center / no-repeat / cover;
    grid-column: 3/4;
    grid-row: 3/4;
}

.destaques__categorias{
    grid-column: 1/3;
    grid-row: 3/4;
}