Pull the line very taut and the hold the line down on the mark with one hand.
Draw straight line on the floor.
Place the level along the line.
The problem is that the width at one end of the room is 290 cm while at the other end of the room is 295 cm so i assume that the walls are not straight.
If the wall is too long to snap the chalk easily kneel by the midpoint of the line and press it down to the floor with one hand.
A chalk line can be as long as needed being.
When any project calls for drawing a long straight line on a floor wall or similar flat surface a professional mechanic will use a chalk line.
Snap the chalk line leaving a straight chalk mark on the subfloor.
This video is about how to make a first straight lane during hardwood floor installation on concrete.
If the bubble goes to the center of the level between the 2 black lines your line is straight.
Use a bubble level as you go to make sure the lines you re drawing are perfectly straight.
Hardwood floor in.