How to delete strings by regular expression?

Question

Notepad++

Good day to all .
Tell me how to remove unnecessary parts from strings using regular expressions and save what you need.
Example strings are always different , in this case the delimiter , the full string looks like ,text,text1,text3,text4,text5 and so on.
What is the regular expression to save text3 and text4
And in the future how to correct it, somehow I tried the regular expression (.*):(.*):(.*): with a replacement for \2:\4: like this, but now even replacing delimiter , on : fails .