Dealing with a large table

I’ve read several forum posts on longtable package, but I’m still really struggling.

I’m trying to insert a table into my thesis, I’ve used https://www.tablesgenerator.com/ to convert my excel table into Latex and from here I’m manually editing.

The problem is, the table is too wide and too tall. I’ve used scriptsize text and I’ve added in the longtable package. I don’t want the table in landscape, so that’s not an option. It’s now breaking over two pages, which I’m happy with. However, I can’t see half of the 3rd column and the 4th one at all.

begin{centering}
scriptsize
begin{longtable}{|c|c|c|c|}
noalign{vspace*{fill}}

*data here*
noalign{vspace*{fill}}
end{longtable}
end{centering}

Additionally, is there a way to centre the text in the middle of the box and make the first column narrower?

Sorry if I’ve missed something obvious, I’ve read the documentation but still can’t get my head around it