Take another read through https://www.mediawiki.org/wiki/Help:Tables
For putting multiple columns in a single line, use !! to separate them for header rows and || to separate for normal rows. If you have formatting, match the ! or |.
{| class="wikitable"
|+ Caption
! scope="col" style="color:red" | Column 1 !! scope="col" style="color: blue" | Column 2 !! scope="col" style="color: green" | Column 3
|-
| data-sort-value="R1C1" | [[R1C1]] || data-sort-value="R1C2" | [[R1C2]] || data-sort-value="R1C3" | [[R1C3]]
|-
| data-sort-value="R2C1" | [[R2C1]] || data-sort-value="R2C2" | [[R2C2]] || data-sort-value="R2C3" | [[R2C3]]
|}
Produces the following:
If that is what you are doing, try doing each column on its own line, or make use of HTML table markup (<table>, <tr>, <th>, and <td>) instead of using wiki markup for tables.