I feel the best way to learn these is by following examples and in every chapter I will take you through several examples showing you different aspects of the function and various uses of it. The examples start with the basic syntax of the function and build up to more complex formulas, but I explain each step along the way. So, don't worry, these are much easier than maybe you think!
CONTENT:
Introduction to functions
Chapter 1 - AVERAGE, MAX, MIN
Chapter 2 - COUNT and COUNTA
Chapter 3 - IF
Chapter 4 - CONCATENATE
Chapter 5 - VLOOKUP (inc IFERROR and ARRAYFORMULA)
Chapter 6 - OR & AND
Chapter 7 - COUNTIF, SUMIF, COUNTIFS, SUMIFS
Chapter 8 - FILTER
Chapter 9 - IMPORTRANGE
Chapter 10 - PROPER, UPPER, LOWER, TRIM
Chapter 11 - TRANSPOSE
Chapter 12 - ISEMAIL, ISNUMBER, ISURL, NOT
Chapter 13 - UNIQUE, COUNTUNIQUE, SORT
Chapter 14 - NOW, TODAY, DAY, MONTH, YEAR, HOUR, MINUTE, SECOND
Chapter 15 - WEEKDAY, WORKDAY, NETWORKDAYS, EDATE, EOMONTH, CHOOSE
Chapter 16 - GOOGLETRANSLATE, DETECTLANGUAGE
Chapter 17 - OFFSET
Chapter 18 - IMAGE
Chapter 19 - ROUND, ROUNDUP, ROUNDDOWN
Chapter 20 - HYPERLINK
Chapter 21 - INDEX and MATCH
Chapter 22 - QUERY