My question is: is there a way to draw precise lines? for example like in autocad - if i want to draw a line with a lenth of 20 i type this value when drawing a line and i want this line to be perpendicular to other line. Im little bit used to that kind of drawing like in autocad: specyfiing values, using features like perpendicular, parallel.
Im not a graphic desinger or anything, just a random guy passing by so please be reasonable and dont make fun of me
Thanks for helping me in advance,
Arek

Welcome aboard!

Inkscape is not a cad program, so there are differences.
The accuracy level is quite enough for precise drawing though, in most cases.

Focusing more on the original problem:
you can draw a two noded straight, horizontal segment with the pen tool, holding Ctrl.
If you use no stroke and use outlines only display mode /switch to geometric bounding box from the visual one in the preferences, it is possible to type in the "length" of the segment into the width field of the object.
Then, you can modify it with "exact" values with the transformation panel (Shift+Ctrl+M).

Making it parallel/perpendicular to other line segments is a bit tricky.
You can convert objects (duplicant of objects) to guide lines (Shift+G), then double click the guide for rotation values. This is only good for three digits -just at the transformation panel-, may not be the most accurate.

Intersecting with a circle as a compass and ruler like construction is no exact either, the best would be to rotate objects until they snap. Not sure if that has been implemented in 0.91.
if so, snap rotation centre and guide line to one of the nodes, and rotate the object until the other node snaps to the guide line.

Short answer.

Yes, Inkscape can be just as precise as CAD programs. But the precision is accomplished in different ways than how the CAD programs work. There may be some functions (maybe even many, I guess, I'm not familiar with CAD wares) of CAD that inkscape just can't do. But speaking only of precision, the only difference is how it's done -- results are the same.