.uk-slider-items {
    justify-content: center;
}

Dont change the settings of the component, leave things on default

.el-marker svg {
/* make the default marker inivisble */
opacity: 0;    
}

.el-marker, .el-marker:hover {
/* Set the general background properties: */
background: transparent center no-repeat;
background-size: 80%;
}

/* add individual icons */
.el-marker:nth-of-type(1),
.el-marker:nth-of-type(2),
.el-marker:nth-of-type(3),
.el-marker:nth-of-type(4),
.el-marker:nth-of-type(6),
.el-marker:nth-of-type(8),
.el-marker:nth-of-type(9),
.el-marker:nth-of-type(12),
.el-marker:nth-of-type(15),
.el-marker:nth-of-type(16),
.el-marker:nth-of-type(17),
.el-marker:nth-of-type(18),
.el-marker:nth-of-type(25),
.el-marker:nth-of-type(26),
.el-marker:nth-of-type(27),
.el-marker:nth-of-type(28),
.el-marker:nth-of-type(29),
.el-marker:nth-of-type(30),
.el-marker:nth-of-type(31),
.el-marker:nth-of-type(32),
.el-marker:nth-of-type(33),
.el-marker:nth-of-type(34),
.el-marker:nth-of-type(35),
.el-marker:nth-of-type(36),
.el-marker:nth-of-type(37),
.el-marker:nth-of-type(38),
.el-marker:nth-of-type(39),
.el-marker:nth-of-type(40)
{
background-image: url(../images/icons/apple.png);
}

.el-marker:nth-of-type(5),
.el-marker:nth-of-type(11),
.el-marker:nth-of-type(13),
.el-marker:nth-of-type(19),
.el-marker:nth-of-type(21),
.el-marker:nth-of-type(23)
{
background-image: url(../images/icons/pear.png);
background-size: 90%;
}

.el-marker:nth-of-type(7),
.el-marker:nth-of-type(10),
.el-marker:nth-of-type(14),
.el-marker:nth-of-type(20),
.el-marker:nth-of-type(22),
.el-marker:nth-of-type(24),
{
background-image: url(../images/icons/plum.png);
background-size: 80%;
}

/* Drop shadow on dropdown submenu area */
.uk-dropbar-top {
box-shadow: 0 8px 8px 0px #00000033;
}

Style > Navbar Nav Item Line > Mode to disable

or enable

change the colour  - hover background / Active background

Change the gap between the line and the menu item here...

YOOtheme > STYLE > Components > Navbar > Nav Item Line > Margin Vertical: ....

Style / Components / Utility / Box Shadow Bottom / Background

Add code into Advanced tab

@media(max-width: 640px) {
    .el-item > .uk-grid {
    display: flex;
    flex-direction: column;
    }
}

Layout > Site > Layout (Boxed) > Add the background image there.

Troubleshooting

For the site in question, replace the current custom CSS you are using by the following CSS. It should remove the background colors of the headerbar, the navbar, all sections and tiles. The background image should be set in the Layout settings, additionally.

.tm-headerbar-top, .uk-navbar-container:not(.uk-navbar-transparent), .uk-section, .uk-tile {
        background: none;
}

Go and play with 

Check if the style has been changed to Primary or Secondary because this will effect which settings are being used.

Then also

Style / Components / Navbar / Dropdown / Color Mode

into Advanced / Classes - add

uk-light