Any way to merge a number of cells into one cell, for example the title of many columns in a table?

Try concat this function joins strings, you can add " " between arguments.
See attached zip

I mean merge the cells so that more than one column is headed by a single cell, I know you can do it with word tables, but I can't find the option in excel. Maybe you can't do it because spreadsheets are less of a presentation tool.. :/

Select the 2 or more cells in the header row and then Format, Cells, Alignment, Check the Merge Cells.