Loading files is much slower than in MicroStation (PowerCivil Ss3)

Dgn files, (Many times made with  MicroStation) which have a lot of models, loads very slow in PowerCivil. It doesn't matter if I open the file or attach it as reference. In MicroStation the same files many often opens direct, while 5 minutes of waiting in PowerCivil is no exception. 

Is there a way to increase the speed?

Thanks in advance,

Louis