I have two line layers, and I want to create a point where they cross each other.
How can I solve it in QGIS?
Based on this answer How to identify line intersection in QGIS when I have more than 2 lines? you can use the built in tool Line Intersections.
Add both line layers to your canvas then from the vector menu select analysis tools then line intersections. Populate the two line layers and the output and hit ok.
Note this tool will not flag self-intersections (where a line crosses itself). The documentation on this tool is very sketchy and a little hard to find but I think it will do what you're after.