I note you suggested this formula
=IF(ISNUMBER(FIND("RuhrP";F9));LOOKUP(A9;Ruhrpumpen!A$5:A$100;Ruhrpumpen!I$5:I$100);"")
.....but LOOKUP
isn't appropriate here because I assume you want an exact match (LOOKUP won't guarantee that and also data in lookup range has to be sorted), so VLOOKUP
or INDEX/MATCH
would be better....and you can also use IFERROR to avoid the IF function, i.e
=IFERROR(VLOOKUP(A9;Ruhrpumpen!A$5:Z$100;9;0);"")
Note: VLOOKUP always looks up the lookup value (A9) in the first column of the "table array" and returns a value from the nth column of the "table array" where n is defined by col_index_num, in this case 9
INDEX/MATCH is sometimes more flexible because you can explicitly define the lookup column and the return column (and return column can be to the left of the lookup column which can't be the case in VLOOKUP), so that would look like this:
=IFERROR(INDEX(Ruhrpumpen!I$5:I$100;MATCH(A9;Ruhrpumpen!A$5:A$100;0));"")
INDEX/MATCH also allows you to more easily return multiple values from different columns, e.g. by using $ signs in front of A9 and the lookup range Ruhrpumpen!A$5:A$100, i.e.
=IFERROR(INDEX(Ruhrpumpen!I$5:I$100;MATCH($A9;Ruhrpumpen!$A$5:$A$100;0));"")
this version can be dragged across to get successive values from column I, column J, column K etc.....