These things are the indication of paths, they can be turned off by clicking the eye icons in the Paths list.
The long diagonal line is however an indication that the text-along-path didn't work properly, this happend when the path is too short for the text.
If you need to do a lot of this, you may want to have a look at https://www.gimp-forum.net/Thread-ofn-text-along-path
The long diagonal line is however an indication that the text-along-path didn't work properly, this happend when the path is too short for the text.
If you need to do a lot of this, you may want to have a look at https://www.gimp-forum.net/Thread-ofn-text-along-path