@J.Hilk Hey, Thank you for all of your help. Solved the problem thanks to you!
If there is anyone facing the same issue, solved like this,
Created a source file named "restarter"
restarter.h
#ifndef RESTARTER_H
#define RESTARTER_H
#include <QObject>
class Restarter : public QObject
{
    Q_OBJECT
public:
    explicit Restarter(QObject *parent = nullptr);
    Q_INVOKABLE void makeRestart();
signals:
public slots:
};
#endif // RESTARTER_H
restarter.cpp (note: my application works as a service named "myservice" on system, so I can not restart it as restarting a regular application.)
#include "restarter.h"
#include <QProcess>
Restarter::Restarter(QObject *parent) :
    QObject (parent)
{
}
void Restarter::makeRestart()
{
    QProcess::execute("sudo service myservice restart");
}
If your application works NOT AS A SERVICE, BUT AN APPLICATION,
restarter.cpp
#include "restarter.h"
#include <QApplication>
#include <QProcess>
Restarter::Restarter(QObject *parent) :
    QObject (parent)
{
}
void Restarter::makeRestart()
{
qApp->quit();
 QProcess::startDetached(qApp->arguments()[0], qApp->arguments()); //application restart
}
You need to register "restarter.cpp" as a QML registery (I know, stupid sentence)
So you need to insert these lines in main.cpp
#include "restarter.h"
qmlRegisterType<Restarter>("closx.restarter", 1, 0, "Restarter");
and use it on your QML file:
import closx.restarter 1.0
Restarter {
        id:restarter
    }
                           Rectangle{
                               id: restartbg
                               width: 120
                               height: 70
                               radius: 8
                               color:"black"
                               anchors.centerIn: parent
                               z:344
                               Text{
                                   anchors.centerIn: parent
                                   text:qsTr("Restart") + mytrans.emptyString
                                   font.family:GSystem.myriadproita.name
                                   font.pixelSize: 18
                                   color: "white"
                               }
                               MouseArea{
                                   anchors.fill: parent
                                   onClicked: {
                                       restarter.makeRestart()
                                   }
                                   onPressed: {
                                       restartbg.color = "#1c1c1c"
                                   }
                                   onReleased: {
                                       restartbg.color = "black"
                                   }
                               }
                           }
Again, thanks to @LeLev and @J-Hilk for everything.