There is a lot to know about tables. I recommend you work by means of table and cell styles. Here is all the helpfile to make sure you are familiar with how it all works and is edited:
Especially the next section about applying cell styles.
In a table, a heading row can be marked as a header, and also have its own cell style. The cell style, in turn has a paragraph style. But no paragraph style for the header can alternate first centered, then left-aligned, then centered, then left-aligned.
So either choose all one or the other, or else make two cell styles for the heading and make one centered and one left-aligned, and then manually apply the cell styles to each column header.
Also, be aware that column widths are not defined by styles at all, so they must be sized manually.