To set up the „Activities” list for your requirements, click on the arrow (triangle) next to „Show/hide columns” in the upper left-hand corner of the screen.
A selection menu appears in which you can hide individual columns by clicking on the respective column names (see screenshot). Columns that are hidden are displayed in grey and crossed out (see screenshot on right). If you want to show hidden columns again, simply click on the respective column names. The column then appears black again and no longer crossed out and is displayed again in your Activity list.