As I cannot tell exactly what question your referring to in your latest post.
how can I define the board shape to be suitable to this enclosure with all screw holes properly set in it?
You either draw it in a dxf file if its a hard shape, or manually with the graphical lines / arcs on the edge cuts layer. This gives you the outside edge of the board,
Next for your mounting holes, as a beginner to the software I would recommend just placing graphical circles on the edge cuts layer in the correct locations,
For Kicad V5, you can use tricks to get everything in the right place, e.g. you know 1 mounting hole needs to be 45mm away from your first one, you can type + or -XXX into the positions for both components or graphical items, for example you might place 1 mounting hole, then duplicate it in the same location and in the Y position type +45mm at the end, and it will do the offset for you.
For the edge cuts layer, the main one is that it should be seamless or the 3D veiwer gets unhappy.
how can I draw in certain dimension like autoCAD for example where you input the length of the line?
At present you cannot type the length and angle of the line in Kicad, but as you draw a graphical line, on the bottom left of the window it will display the angle and the length of the line.
And finally, if it will fit in the enclosure,
As it doesnt give any solid dimensions, your best bet would be to ask the manufacturer for a dimensioned datasheet for the enclosure, as even the spacing between mounting holes appears to be a guessing game at this point.