Thymeleaf if else [duplicate]

I don't know how to wrote this kind of insruction using Thyeleaf. I've got my view made with html.

<#if updateClient??>
        <h2>Modifica del prodotto - ${updateClient.nome}</h2>
        <div style="margin: 20px;">
            <form method="POST" action="update" id="updateClient">
                <input type="hidden" name="id" value="${updateClient.id}"/>
                <div>
                    <label for="name">Name</label>
                    <input type="text" name="nome" id="nome" value="${updateClient.nome}" />
                </div>
                <div>
                    <input type="submit" name="invia" value="Update" />
                </div>
            </form>
        </div>
    <#else>
        <h2>New Client</h2>
        <div style="margin: 20px;">
            <form method="POST" action="add" id="newDataClient">
                <div>
                    <label for="nome">Nome</label>
                    <input type="text" name="nome" id="nome" value="" />
                </div>
                
                <div>
                    <input type="submit" name="invia" value="Add" />
                </div>
            </form>
        </div>
    </#if>

This was written using FreeMarker, but I need to use Thymeleaf. I know simple Thymeleaf instructions, but I don't know how to do this. I read Thymeleaf instructions, and I find how to iterate a list of variables, but not how to create this structure using if and else. And if it's possible create something like this.