When I try to draw a rectangle, it does not appear. I can fill it but I don’t want to. I just want a normal rectangle with borders. How to do it?
You need to add a stroke to the rectangle.
To do it, open the Fill & Stroke panel Shift+Ctrl+F, choose the Stroke Paint tab to choose a colour, and then in the Stroke Style tab, choose a suitable width of stroke. Note: if the width of stroke is set to 0, it won't be visible.
It's also possible to set the stroke colour and width by right clicking on the stroke colour box, or width shown at the bottom of the main window.
You can also Shift+Click a colour on the colour palette to set the stroke colour.