Oh for gods sake..... Use the search facility or even better read the documents that relate to the legislation that you fly under. Something that you have a LEGAL responsibility to do. You could start with LASORS or whatever the authority you fly under(germany?) has as an equivalent.
No you cant log anything for twiddling the knobs on the radio or looking out of window on a single pilot aircraft. The pilot is commander of a single pilot aircraft should be able to operate the aircraft without any assistance from you. If he can't then perhaps he should hand his license in......
If you want to split the time then agree at what point the PIC role is handed over. If you are doing this in the air then get some training on flying from the RHS. Is it a little different, as Instructors we are trained for it, as a low hours pilot (which your question seems to indicate) you need some practice to do this.