@if (SignInManager.IsSignedIn(User))
{
    <form asp-area="" asp-controller="Account" asp-action="Logout" method="post" id="logoutForm" class="navbar-right">
        <ul class="nav navbar-nav navbar-right">
            <li>
                <a asp-area="" asp-controller="Manage" asp-action="Index" title="Manage">Hello @UserManager.GetUserName(User)!</a>
            </li>
            <li>
                <button type="submit" class="btn btn-link navbar-btn navbar-link">Log out</button>
            </li>
        </ul>
    </form>
}
else
{
    <ul class="nav navbar-nav navbar-right">
        <li><a class="btn btn-primary btn-block navbar-header" asp-page="/TourAnbieten">Tour anbieten</a></li>
        <li><a asp-area="" asp-controller="Registrieren" asp-action="Create">Anmelden</a></li>
        <li><a asp-area="" asp-controller="Login" asp-action="Details">Einloggen</a></li>

        @*<li><a asp-area="" asp-controller="Account" asp-action="Register">Register</a></li>
        <li><a asp-area="" asp-controller="Account" asp-action="Login">Log in</a></li>*@
    </ul>
}

if(condition == true)
            {
                //show logged in partial

            }