5. I have a column containing numbers, but it appears with a text format. What should I do?
Probably, there is a cell in the column containing a letter or a symbol (or there has been one at some point in the past). You can change the data type to a numeric format doing:
Data > Change Data Type > Text to Numeric
Observe that in text columns a T appears next to the column and their values are aligned to the left. Numeric columns, however, are aligned to the right.