div.mainStructure {
    display: flex;
    justify-content: center;
    width: 75%;
}
div.mainElements{
    width: 100%;
}
div.mainElements:not(:last-child) {
    margin-right: 50px;
}

@media screen and (max-width: 1300px) {
    div.mainStructure {
        width: 100%;
        display: flex;
        flex-direction: column;
        justify-content: center;
    }
    div.mainElements:not(:last-child) {
        margin-bottom: 50px;
    }
}

/*-----------------------------------------------------------------------*/
.mainHolderElement {
    width: 75%;
    display: flex;
    flex-direction: column;
}
.cardsHolderElement {
    display: flex;
    justify-content: center;
}
.cardExtElement {
    width: 33%
}
.cardExtElement:not(:last-child) {
    margin-right: 50px;
}
.flexColAndCenter {
    display: flex;
    justify-content: center;
}
@media screen and (max-width: 1300px) {
    .mainHolderElement {
        width: 100%;
        display: flex;
        flex-direction: column;
    }
    .cardsHolderElement {
        display: flex;
        flex-direction: column;
        justify-content: center;
    }
    .cardExtElement {
        width: 100%
    }
    .cardExtElement:not(:last-child) {
            margin-bottom: 50px;
    }
}

.cardExtElementAbout {
    width: 50%
}
@media screen and (max-width: 900px) {
    .cardExtElementAbout {
        width: 100%
    }
}