Group table lines with cell content

[Farlif]

Hello, absolut newbie here, I've got a table with 1600+ lines, and 20+ columns. Now I want to sort them according to "cell content contains word 'keyword' in column F", or better, mark those which contain my text string in column F with an x in column I.
Please, how can I do that? 

EDIT
34 views ... Obviously I'm wrong here with my newbie question. Sorry! 
Wish you great holidays! 

Excel 16.68
Mac OS Ventura 13.0.1

[#2]

Well, probably too easy for you all. :)
I tried =IF(SEARCH("auf",F2,1), x, "") in several variations, but I always get an error message that there's a problem with the function. Can you help me?

[#3]

Post few sample data and desired output. Better to attach a sample file. We can't understand what your are trying to achieve from your post. So, to illustrate it better way attach sample having desired result.

[#4]

Close but you might have luck with this:
=IF(ISNUMBER(SEARCH("auf",F2)),"X","")