problem with sheets

hello all,
i have to work on a .xlsx sheet in google drive. this sheet is shared with a group of people so the work must be done online and not on my private pc. therefore i downloaded the sheets app to my iphone. the problem is i can see all the rows but only the first 4 columns from a to d
i know that there are more because when i opened the sheet with my pc it showed 10 columns.
so what should i do to view all the columns of the sheet on my iphone? when i tried to slide left or right it just took me to the next row. for example if i stood on square d1 and slide to the left it took me to c1 if i slide to the right it takes me to a2 and not to e1.
thanks for your help
tal