grammar issues on worksheets

If you use workbooks, you can edit the worksheets after adding them to one of your workbooks. Also, if you want the creator of the worksheet to correct the mistakes you can go to "Post a new comment", the creator of the worksheet will receive your comment (it's at the very end of the page).

You can edit other users' worksheets only if you add them to your workbooks. In that case, you can go to my workbooks, open the workbook, choose the page and click "Edit". There you can edit the interactive part of the worksheet (right answers).