again an update 
I have converted the data to raw data and did manage to get a PSD. my question now is, how can I know that my artifacts are really gone? i had also before i wanted to remove the artifacts also applied and resampled a bandpass filter. does it remain present if i worked with the raw data on which i resampled and applied a band pass filter? or do you need to remove the artifacts first and only then apply the bandpass filter.