Can someone explain to me how to use these three options I marked below
Hi Chukwudalu,
thanks for your question.
The mapped mesh preferred option tries to align the FE mesh with the boundary lines of surfaces. This option can be set globally for all surfaces (first option) or defined individually for each surface (second and third option).
The following image is from the RFEM 5 manual ( rfem-5-manual-en.pdf, p 298):
If you have any further questions, just ask. I am happy to help 
Best regards
Clemens Gutmann
Thank you for your reply, so what is the difference between the second and the third option
If the second option is selected, the mapped mesh will be preferred for this object, and if the third option is selected, the mapped mesh will not be preferred for this object. Both options override the global setting for the mapped mesh.
If you have any further questions, just ask. I am happy to help