Help with a few issues im having with lightburn

Im new to light burn and have a few questions

First I have an Ortur Laser master 2 and the work space is 400mm x 430mm. When I go to change this in lightburn the option is grayed out, how do I fix this? (picture included)

Second, when I trace an image and zoom in I see that some of the lines are not straight, how can I fix this (picture included)

Third, when I try and resize an image with the width height tool in mm it does not seem to be accurate in size when it cuts. I messure the size I want lets say its 2.5 inchs and when it laser engraves it does not come out 2.5 inchs

Thanks for the help

You have the wrong ‘Device Profile’ selected. You will need to delete that profile and build another, correct one for your setup. The one chosen, “Emblaser 1 A3” is for a different system entirely, which has a fixed and known bed size. Using this profile, there is no need to change the bed size, ever, so it is grayed. You should be using the GRBL profile, which allows bed size adjustment. Adding a Laser - LightBurn Software Documentation