I already have the bezier tool taking different forms, for example, when I draw a straight line, sometimes it doesn't change the width, I can't zoom in or out, then after I finish the line, sometimes it becomes invisible, it can't be restored, sometimes after I finish drawing a thin line, the line suddenly grows.
When you use the Bézier tool in Inkscape, the normal behaviour is for it to show only the path outline while you are drawing. When you finish with the tool by pressing Enter, or close a path, Inkscape will display the stroke if one is set, or nothing if no stroke is set. Nothing is broken here. This is how the tool is supposed to work.
If a stroke does not become visible after you have used the Bézier tool, it could mean that you have no stroke set, or the Opacity or the Alpha could be set to zero. You can add strokes and fills to a path using the Fill and Stroke panel.
If a the path suddenly shows a thick stroke after using the Bézier tool, you can change the stroke width in the Stroke Style tab.
The Fill and Stroke panel Shift+Ctrl+F
This is very basic functionality in Inkscape. What I would suggest you do is follow some basic tutorials first. There are many on youtube which should help you become familiar with the basic tool operations and the user interface. Inkscape is not easy or intuitive. It's a complex tool. You have to learn to walk before you can run.