My respected teachers,
''No rush because we are going on bypass.'' Correct it please
''We are going OR walking by road.'' means?
''Get a wire fence built around your roof.'' Correct it please
(4) Get a cemented fence built around your roof.'' Correct it please
"I invited her for a dinner.'' OR ''I invited her to a dinner.''?
(1) needs more context. It could mean several different things. It is unclear here.
(2) should either be "we are driving" or "we are walking" - you don't need "by road" as that is obvious. If you are not actually driving, then "we are going by bus" or "or we are being driven" or whatever.
(3) needs more context, too. It could mean several different things. It is unclear here. If it is a simple imperative, then it is correct.
(4) if the question is of the word cemented, then you should replace it with concrete. Cement is one of the ingredients in concrete, and by itself is a powder, and not very useful in fencing. (Cement is also glue, as in plastic model cement, but that wouldn't build much of a fence, either.)
(5) Probably, you invited her to dinner. If you say to "a" dinner, then it implies something a little more specific, as if you wanted her to taste the cuisine, rather than to share your company. I suppose that you could invite her for dinner as well as to dinner; in my mind the for limits your engagement to dinner and nothing else. I would keep your hopes higher and invite her to dinner and see what comes of it later.