Hi Verena, there are only a few areas within the printer for you to clean, Best thing to use a can of computer foam cleaner, you don't need a lot just spray it on some tissue, the key areas to clean is the strip at the back of the printer, please treat it gently. When the ink carriage moves over, you can turn it off, and clean the round pads, these tend to build up with a lot of ink, and so tissue to absord excess ink and to use a little bit of foam cleaner to clean the unit. Where the little red light sensor, it may need a good wipe.

You do not want to spray the foam into the machine as this will remove lubricating grease which the machine needs to run on.

Kind regards

Steve