JSFiddle - React, Tailwind, and code Playground

HTML

<div id="base">
    <section style="color: black;">
        <div class="leftMain"><div id="leftmenu">
            <div class="titlebox"><div class="text"><?php echo NOM_SITE;?></div></div>
            <ul>
                <li><a href="#">DATA</a></li>
                <li><a href="#">DATA</a></li>
                <li><a href="#">DATA</a></li>
            </ul>
        </div>


        <div id="leftmenu">
            <div class="titlebox"><div class="text">MENU</div></div>
            <ul>
                <li><a href="#">DATA</a></li>
                <li><a href="#">DATA</a></li>
            </ul>
            </div>

        <div id="leftmenu">
            <div class="titlebox"><div class="text">MENU</div></div>
            <ul>
                <li><a href="#">DATA</a></li>
            </ul>
            </div>

        </div>

        <div id="rightmenu">
            <div class="titlebox"><div class="text">MENU</div></div>
            <div class="droite_text">
                <li><a href="forum.php?id=1">DATA</a></li>
            </div>
        </div>

        <div id="rightmenu">
            <div class="titlebox"><div class="text">MENU</div></div>
            <div class="droite_text">
            DATA
            </div>
        </div>

CSS

#leftmenu {
    margin-left:5px;
    margin-top:5px;
    height:auto;
    width:150px;
    background-color:gray;
    padding:2px;
}

#leftmenu .titlebox {
    height:20px;
    width:150px;
    background-color:black;
}

#leftmenu .titlebox .text {
    margin-left:10px;
    font-family:OswaldL;
    font-size:14px;
    color:white;
}

/*Now, here is the part that I want to move to the upper right side*/

#rightmenu {
    margin-left:5px;
    margin-top:5px;
    height:auto;
    width:250px;
    background-color:gray;
    padding:2px;
    float:right;
}

#rightmenu .titlebox {
    height:20px;
    width:250px;
    background-color:black;
}
.leftMain{
    
    float:left;
}
#rightmenu .titlebox .text {
    margin-left:10px;
    font-family:OswaldL;
    font-size:14px;
    color:white;
}