Documentation for Guizero is here: https://lawsie.github.io/guizero/, click on the Widgets menu dropdown. I find it pretty good.
Using guizero is simple but not easy. It does what it does but, it is difficult to get it to do what you really want it to do.
I find that one has to constrain objects in guizero, to stop them deciding themselves where they want to be, by putting them in boxes in each functional area of your form. In your case the left and right boxes need to be in a "middle" box between your top and bottom boxes. This gets rid of the extra space.
I also find that I need to add padding to stop objects being too close to edges and to each other, and to force the layout, for example, in grid layout. For padding I use a "Text" widget with empty text, and control its size with the width and height properties which are character sizes for the text widget.
I have made a rough example of what you said that you wanted. Note the middleBox, and the padding "Text" widgets especially around the buttons in the grid. Note also that the option and input text varies position in spite of being left aligned, ah well.
Form produced by the code below
from guizero import App, Text, TitleBox, Box, TextBox, CheckBox, PushButton
app = App(title="Restaurante")
app.width = 1280
topHeight = 100
middleHeight = 500
bottomHeight = 100
app.height = topHeight + middleHeight + bottomHeight
rightWidth = 380
leftWidth = 900
app.width = rightWidth + leftWidth
paddingHeight = 1
topBox = Box(app, align="top", width= "fill", height= topHeight, border= True)
padding01 = Text(topBox, text="", height = paddingHeight)
message = Text(topBox, text="TOP BOX", align="top", height = 1, size = 18)
padding02 = Text(topBox, text="", height = paddingHeight)
#messagel = Text(app, text="DeLeitese con nuestros exquisitos pLatos")
middleBox = Box(app, align="top", width= "fill", height= middleHeight, border= True)
leftBox = Box(middleBox, width= leftWidth, height= middleHeight, border= True, align="left", layout="grid")
inputLabel01 = Text(leftBox, text="Input01", grid=[0,0], width = 20, size = 14, align="left")
inputText01 = TextBox(leftBox, text="Type Input01 here", width = 40, grid=[1,0])
inputLabel02 = Text(leftBox, text="Inp02", grid=[0,1], width = 20, size = 14, align="left")
inputText02 = TextBox(leftBox, text="Type Inp02 here", width = 40, grid=[1,1])
inputLabel03 = Text(leftBox, text="Input03", grid=[0,2], width = 20, size = 14, align="left")
inputText03 = TextBox(leftBox, text="Type Input03 here", width = 40, grid=[1,2])
rightBox = Box(middleBox, width= rightWidth, height=middleHeight, border= True, layout="grid")
option01 = CheckBox (rightBox, text="", width = 2, grid=[0,0])
option01Text = Text (rightBox, text="Option01 ", width = 30, align="left", grid=[1,0])
paddingOpt01 = Text(topBox, text="", height = paddingHeight)
option02 = CheckBox (rightBox, text="", width = 2, grid=[0,1])
option02Text = Text (rightBox, text="Option02 is really gigantic ", width = 30, align="left", grid=[1,1])
paddingOpt02 = Text(topBox, text="", height = paddingHeight)
option03 = CheckBox (rightBox, text="", width = 2, grid=[0,2])
option03Text = Text (rightBox, text="Option03 ", width = 30, align="left", grid=[1,2])
paddingOpt03 = Text(topBox, text="", height = paddingHeight)
bottomBox = Box(app, align="top", width= "fill", height= bottomHeight, border= True)
leftBottomBox = Box(bottomBox, align= "left",width= leftWidth, height= bottomHeight, border= True, layout = "grid")
paddingBot00 = Text(leftBottomBox, text="", width = 20, height = paddingHeight, grid = [0,0])
paddingBot10 = Text(leftBottomBox, text="", width = 20, height = paddingHeight, grid = [1,0])
message = Text(leftBottomBox, text="LEFT BOTTOM BOX", grid = [2,0])
paddingBot01 = Text(leftBottomBox, text="", width = 20, height = paddingHeight, grid = [0,1])
buttonOK = PushButton(leftBottomBox, text="OK", width = 20, height = 1, grid = [1,1])
paddingBot21 = Text(leftBottomBox, text="", width = 20, height = paddingHeight, grid = [2,1])
buttonCancel = PushButton(leftBottomBox, text="Cancel", width = 20, height = 1, grid = [3,1])
rightBottomBox = Box(bottomBox, align= "right",width= rightWidth, height=bottomHeight, border= True)
message = Text(rightBottomBox, text="RIGHT BOTTOM BOX")
app.display()