Cylinder head gasket? Slime and low water level 2.0d

Moin people. New problem Checked today the oil level on the V50, 2.0d from 2005. Oh shock: oil level at the maximum. OK, “701-deckel” opened and in the complete filling tube white/yellowish mucus cooling water level checked: ~1cm below minimum, no oil in the water When driving I did not notice anything the last days. Drive every day 35km easy distance over federal and country roads, partly local passes. Regeneration etc. one noticed clearly when he carried it out – there has Two months ago, he hung on to the tester – without an entry. Is my ZKD going through? Oil increase? Next steps to limit the error? Does anyone know a good workshop in the Diepholz or Vechta circle? Thank you for your answers.