in terminal in your home directory issue the below command
sudo gedit ~/.gtkrc-2.0
and copy the below content and save
style "gtkcompact" {
GtkButton::defaultborder={0,0,0,0}
GtkButton::defaultoutsideborder={0,0,0,0}
GtkButtonBox::childminwidth=0
GtkButtonBox::childminheigth=0
GtkButtonBox::childinternalpadx=0
GtkButtonBox::childinternalpady=0
GtkMenu::vertical-padding=1
GtkMenuBar::internalpadding=0
GtkMenuItem::horizontalpadding=4
GtkToolbar::internal-padding=0
GtkToolbar::space-size=0
GtkOptionMenu::indicatorsize=0
GtkOptionMenu::indicatorspacing=2
GtkPaned::handlesize=4
GtkRange::troughborder=0
GtkRange::stepperspacing=0
GtkScale::valuespacing=0
GtkScrolledWindow::scrollbarspacing=0
GtkExpander::expandersize=10
GtkExpander::expanderspacing=0
GtkTreeView::vertical-separator=0
GtkTreeView::horizontal-separator=0
GtkTreeView::expander-size=8
GtkTreeView::fixed-height-mode=TRUE
GtkWidget::focuspadding=1
}
class "GtkWidget" style "gtkcompact"
style "gtkcompactextra" {
xthickness=2 ythickness=2
}
class "GtkButton" style "gtkcompactextra"
class "GtkToolbar" style "gtkcompactextra"
class "GtkPaned" style "gtkcompactextra"
if you increase xthickness and ythickness it will make menus bigger so value 2 is fine