Can someone explain to me please how can I join a data base that i have in an Excel Sheet and i want to put it in a ArcGis Pro data base. I know that the tool that i need to use is "JOIN"
Could this help you:
Grundlagen des Verbindens von Tabellen—Hilfe | ArcGIS Desktop
You cannot add Excel spreadsheets to ArcGIS pro if they are newer than Excel '97 or something like that. Your best option is to use catalog and import the excel spreadsheet as a table or convert the .xls to .csv