$qb = $this->_em->createQueryBuilder()
    ->select('partial s.{id, activity}, partial a.{id, title}, partial p.{id, evaluationType}')
    ->from('InnovaPathBundleEntityStep', 's')
    ->leftJoin('s.activity', 'a')    //join on Activity entity
    ->leftJoin('a.parameters', 'p')  // join on ActivityParameters entity
    ->andWhere('s.path = 2')
;

/**
 * @ORMTable(
 *     name="claro_activity_evaluation",
 *     uniqueConstraints={
 *         @ORMUniqueConstraint(
 *             name="user_activity_unique_evaluation",
 *             columns={"user_id", "activity_parameters_id"}
 *         )
 *     }
 * )
 */
class Evaluation
{
    /**
     * @ORMManyToOne(targetEntity="ClarolineCoreBundleEntityUser")
     * @ORMJoinColumn(onDelete="CASCADE", nullable=false)
     */
    protected $user;

    /**
     * @ORMManyToOne(targetEntity="ClarolineCoreBundleEntityActivityActivityParameters")
     * @ORMJoinColumn(name="activity_parameters_id", onDelete="CASCADE", nullable=false)
     */
    protected $activityParameters;

    /**
     * @ORMColumn(name="attempts_count", type="integer", nullable=true)
     */
    protected $attemptsCount;

}

/**
 * @ORMTable(name="claro_user")
 * @ORMEntity(repositoryClass="ClarolineCoreBundleRepositoryUserRepository")
 */
class User
{
    /**
     * @var integer
     *
     * @ORMId
     * @ORMColumn(type="integer")
     * @ORMGeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @var string
     *
     * @ORMColumn(name="first_name", length=50)
     * @AssertNotBlank()
     */
    protected $firstName;

}

/**
 * @ORMEntity
 * @ORMTable(name="claro_activity_parameters")
 */
class ActivityParameters
{
    /**
     * @var integer
     *
     * @ORMId
     * @ORMColumn(type="integer")
     * @ORMGeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @var ClarolineCoreBundleEntityResourceActivity
     *
     * @ORMOneToOne(
     *     targetEntity="ClarolineCoreBundleEntityResourceActivity",
     *     mappedBy="parameters"
     * )
     * @ORMJoinColumn(name="activity_id", onDelete="CASCADE", nullable=true)
     */
    protected $activity;

    /**
     * @var string
     *
     * @ORMColumn(name="evaluation_type", nullable=true)
     */
    protected $evaluationType;

    /**
     * @return string
     */
    public function getEvaluationType()
    {
        return $this->evaluationType;
    }
}

/**
 * @ORMTable(name="claro_activity")
 */
class Activity
{
    /**
     * @var string
     * @ORMColumn(length=255, nullable=true)
     */
    protected $title;

    /**
     * @ORMOneToOne(
     *     targetEntity="ClarolineCoreBundleEntityActivityActivityParameters",
     *     inversedBy="activity",
     *     cascade={"persist"}
     * )
     * @ORMJoinColumn(name="parameters_id", onDelete="cascade", nullable=true)
     */
    protected $parameters;

    /**
     * @return string
     */
    public function getTitle()
    {
        return $this->title;
    }
}

$qb = $this->_em->createQueryBuilder()
    ->select('partial s.{id, activity}, partial a.{id, title}, partial p.{id, evaluationType}')
    ->from('InnovaPathBundleEntityStep', 's')
    ->leftJoin('s.activity', 'a')    //join on Activity entity
    ->leftJoin('a.parameters', 'p')  // join on ActivityParameters entity
    ->andWhere('s.path = 2')
    ->leftJoin('?i dont know what?', 'e')  // join on Evaluation entity
    ->andWhere('e.user = 3')      //data for a specific user
;