I am using joomla Catalyste Tamplate V. 3 and I am not expert .. just a simple user .. I tried all the parameters of K2 that will show or hide the list of categories I made at the page side .. I failed .. any body can help to where I will go and show or hide or settle an option to show a list of the categories and tags I create in one column.
Thanks. The page is only showing like that though I apply K2 default CSS and not my template defaults

for a single column try this
Category settings
leading items 0
primary items 10 or as you choose and set columns to 1
secondary items 0

in the item view in category settings set everything to hide except the title
you should get a one column list with titles and links to items.
add back whatever you want to show in the list