Do you want to filter or do you want to sort?
If you want to filter click "Data" then "Filter". Small arrows will appear at the top of each column. Click the one in the column where "Slow" can be found. You will see an option "Slow". Click on that and only your "slow" rows will be shown. Note that this does not gather together your slow entries. You will note from the row numbers that they are not consecutive. The rows without "slow" will be hidden.
If you really want to gather your "slow" entries together you need to sort the spreadsheet. To do this click "Data" then "Sort". Your data will be highlighted and a dialogue box displayed. In that box you need to choose the column containing "slow". Choose that and the data will be sorted. Your "slows" will then appear together.