Dear Abna,
ad 1.: please follow ATENA Troubleshooting, 2.1.1 to send us your model + the calculated Load-Displacement graph such that we can help you identify the problem source.
You can also first try yourself to check for the most common issues following Troubleshooting, 2.2.18 My analysis results do not match the experiment/expectations. How can I improve my model?

Ad 2.: If you seek help with a particular modelling, please send us some sketches + description (Troubleshooting, 2.1.1) such that we can help you finding an efficient way of modelling.

Ad 3.:  For displaying moments (and other cross-section based results), see ATENA Engineering 2D User's, 4.7.5 Moment Lines and 8.3 Internal Forces or ATENA Studio User's, 3.7.1.3 Results "Evolution 1D" and 3.7.2.1 Cuts and 4.2.1 Cuts – Forces and moments (depending on which of the GUEs you work with).

Even if you prepare your model in ATENA Egr 3D, you can postprocess the results in ATENA Studio - to export the binary result files from ATENA Engineering 3D, see ATENA 3D User's, 5.3.3.2 Result Manager and 5.3.3.3 Save Step Results, then import them into ATENA Studio (Create new project from result files).

Regards.