I want to know if there are any ressources from them I can take some functions for calculated columns in SharePoint. I found this article MS Site there are some functions, but not the functions NOW(), TODAY(). So my question is, is there a complete list of functions I can use for calculated columns? Thanks!
Danny Engelman has a very good list for tested and tried functions for calculated column.
You can view the list here: http://www.viewmaster365.com/365coach/#/Calculated_Column_Functions_List
You cann't work with columns like Today() or Now() in calculated columns. But calculated columns can be handy in many scenarios, i.e. If you have fields like lets say, red, green, yellow indicators, you can easily use HTML in calculated columns to show, red, yellow or green images based on categories.
Also, you can play around with mathematical calculations based on other columns but one point to note that calculated columns only work with current row/ list item. they do not work with the values of different rows, it means you can't get summation or aggregations of values for calculated columns.
There's a great Dev Center resource that provides a list of Calculated Field Formulas. I've used it to calculate date values, do basic math, and concatenation.
Calculated columns cannot contain volatile functions like Today and Me.
You can use Excel to built the formulas and use it in SharePoint.