I'm not entirely sure what this is referring to - perhaps "marking tool" is a translation issue?
A video or screenshot demonstrating the issue could also be useful
the selection tool is fairly difficult to use because it "remembers" the last selection and if you then switch to another tool you can not use those tools until you have deselected the selected area, and it can be quite difficult if you have to hold on and resize the selection
I'm not entirely sure what this is referring to - perhaps "marking tool" is a translation issue?
A video or screenshot demonstrating the issue could also be useful