Ok I will describe it most precise:
I have a feature class from a downloaded .gdb consisting of polygons in the whole Netherlands. I clip it to two municipalities so I have two feature classes inthe Project.gdb . These two feature classes behave normal and I can switch symbology on all categories normally for example.
Then i join a standalone table to one of these feature classes (standalone table: 50.000 records, feature class 100.000 records). The joining itself is done in a few seconds but if I then want to work with the feature class for example cahnge the symbology to another category it takes hours before this action is performed. A solution is to run the feature to feature class tool and then I get a new feature class and this one acts normal. The running of this feature class to feature class tool takes 2 hours. I think this has to do with the indexing, am I right? Would you know why it takes so long?