i also have one with 75 but i think there is limit so what should it be?

I just got up to 167 before I stopped testing. If you are receiving the "an unexpected error occurred" message, it's not because you reached a column limit, it's because there is an issue with one of the fields you added.

but when we see the preview or result of saved search then how many coloumns we can see or showing at the same...what limit it is?? for results coloums there is so many in the backend query...but when we can see that then how much coloumn limitations it has??

I'm curious what your use case is. I don't think NS has any technical limit, but for practical purposes anything over a few dozen starts to get really cumbersome to deal with. Unless you're using this as an export to another system?