Mesh loft quality and mesh union (C++)


So I created a loft between two cylinder-like pieces of mesh, and I have two questions regarding the outcome:
1- How can I increase the quality of the loft mesh. As in adding more triangles to make it more smooth? (See Image below).

2- How can make a union of all three meshes so that I have one uniform and connected mesh, without seeing the separation lines between the loft and the other meshes? Probably a function to remesh the combination of all three parts to form one unique part without those orange curves ? (See Image below)


Thank you

Do you see those when you are in render mode ? Above you can chose Wireframe, Shcaded, Rendered.