Customize the search field in Essential Grid

Hey

I’m doing the new website of my collective
Here is the beta version : https://www.collectifsaga.com/X/wordpress

My home is made out with the plugin Essential grid, that works pretty well

I just have an issue with the search field, on the top right of the page.
I want to custom it

The problem is that I don’t know how to do it, because I don’t know if I have to edit the CSS of WP or the CSS of Essential grid.

I want to change the color of the background. I guess I will manage to do it. last time I succeed but editing the WP CSS, so I change the color of all the forms fields

My big problem is the two buttons, that I want to place after the search field and not underneath it.

Third problem : the text “find …” is not in the middle of the field but at the top, and I didn’t manage to change it.

Do you think you could help me with that ?

Here is the CSS of Essential Grid (settings.css)

/******************************
    -    SEARCH FUNCTION    -
********************************/
input.eg-search-input[type="text"],
.eg-search-input    {
            font-weight: 100;
            display:inline-block
            }

.eg-search-submit,
.eg-search-clean    {
            font-weight: 100;
            display:inline-block;
            width:auto;
            -moz-user-select: -moz-none;
            -khtml-user-select: none;
            -webkit-user-select: none;
            }

.eg-search-submit,
.eg-search-clean    { cursor: pointer}

.eg-search-wrapper
            {
            vertical-align: top;
            line-height:15px;
            width:15%;
            }

input.eg-search-input[type="text"]
            {
            font-family: "Times",serif;
            font-size:9px;
            outline:none !important;
            margin:2px !important;
            padding:2px;
            vertical-align: bottom;
            }

Thanks for your help