If you draw a line as straight as is practically possible on a curved surface then in three dimensions it will be curved. But in local terms the curvature disappears in the "noise" of not having anything perfect. Perfection is a concept only.
We can conceive something perfectly straight, and we can understand we are unlikely to find this in practice, even light will bend.
As others have mentioned, you appear not to go logically from this issue of straightness to Newton's laws. If there is a connnection we have not spotted then you will need to give us more details.