I finally found a solution!!! 😄
I installed Dconf Editor from the software center and I went through org.gnome.settings-daemon.plugins.overrides and i set it from {'Gtk/ShellShowsAppMenu': <0>, 'Gtk/DecorationLayout': <'menu:minimize,maximize,close'>} to {'Gtk/ShellShowsAppMenu': <0>}. This way gnome tweaks works perfectly. 😁
I hope it's going to be helpful and thank you for your reply. 😃