help needed edges offsetsrf.3dm (18.7 MB)
Screenshots are by and large useless. Post your 3D file if you want concrete answers regarding your specific model and problem.
i added it to the post now. i apologize, im new to this forum
If you build proper curves (without kinks), and then proper NURBS surfaces (without kinks), you can join them and offset solid, if this is what you want - but if you offset too much, you get what you see on the right.
To add to what @Lagom has said, this is a common issue not exclusive to Rhino. When the offset is larger than the radius at an interior corner (minimum radius of curvature) the offset may fail or produce unwanted results. The alternative is to recreate the problem area not using an offset, or to consider a mesh only result, such as ShrinkWrap if your end use allows a mesh.
This is one of those things that you can easily blunder into when you first use offset, but after you see the explanations on the forum and give it a bit of thought you just say to yourself “duhhh”, give yourself a head-slap and start modelling the “inside” surface first and offset only to the “outside”. That is, start with the surface having the smallest radii and offset to the larger radii side.