polilinea

hello i try to learn the polilinea

 but i  only make line straight,

 if i wont to make an  arc  after the line

with polilinea what is it the process?

Look at the tool options tool bar, it's above the drawing area.
When the polyline tool is active, you have additional items there to change between line and arc and other options.
See https://librecad.readthedocs.io/en/latest/ref/tools.html#polyline

But sometimes it may be easier to build a contour with lines and arcs and then create a polyline from existing segments. This is the last tool in the polyline menu.
It is important, that the segment endpoints match exactly, otherwise the tool doesn't work correct.
You can use the command line for exact coordinates or use valid snap modes to achieve this.

Armin