Thanks a lot for the hint!
This made the trick:
out = torch.squeeze(torch.nn.functional.conv1d(out.view(1, Nv, -1),
                                        torch.flip(Cp,dims=(1,)).view(Nv,1, -1), 
                                        padding=(Nt - 1), groups= Nv))

Now I am haveing problems with the fact the during curve fitting 2 out of 4 parameters are not updated, but I guess that’s another separate issue … -.-"