how can i remove dotted lines. i cannot push or pull as a whole.
How did you create them? Normally, if the surface is flat, those edges are not necessary and do not appear (are not created automatically).
What happens if you delete them?
it appeared after i used smooved tool of sandbox. i used its at one place but this line appeared in all model.
i need to delete it one by one. thats a long time
Using the Smoove tool you most likely distorted the geometry, so if you delete them, the faces will be deleted too. Either resume modeling before Smoove and depending on what you want to achieve use an appropriate tool, or you can try to flatten the faces using an extension (Vertex Tools).
Turn off hidden geometry?
that is not hidden geometry
SARANGKOT-17-12-2025-base.skp (14.3 MB)
you can only see these lines if you double click and select the model
thank you. i know it can be erased. But i was expecting some plugin. Erasing is taking a long time
so they are hidden. one could even call them hidden geometry 
two ways to see hidden geometry are either like mike described, turning it on in the menus, or selecting all of a model (triple click on it will do it)
and that’s a good thing. SU tells you “by the way, you have hidden lines here”. and as soon as you unselect, they’re back to hidden.
some, like Mihail said, are not needed, when you erase them, no face disappears.
some other are needed, because not everything in your model is perfectly coplanar. erasing them will make holes in your model. keeping them makes your model look clean and flat even if it isn’t
check cleanup by thomthom
it has some preset cleanup modes including one that will merge all coplanar faces. it’ll get rid of the non-needed hidden lines
clean up did not erased the lines . but i removed them manually. thank you so much. i think the problem was solved. 
Please buy a license to SketchUp.
sure. i am using licensed sketchup