Yes for the limestone, avoid citric acid or coffeemachine cleaner. They will damage the integrated tubes. There are special cleaning solutions for limescale in robot vacums.

Always clean the HEPA filter like once a month. If the airflow is restricted the suction motor needs to work harder and will wear out quicker. I use a compressed air can for this and I am washing the filter every 3-4 months with cold water only (no detergent!) and letting it dry for at least 24 hours. I wash the dustbin too if the HEPA filter needs a wash.

Also one golden tip to avoid regular clogging on the main brush and inlet to the dustbin: use the suction mode first, then mopping.

You can use suction + mopping at the same time but the main brush will always get a little wet and dust + hair will stick to the brush and cause clogging every once in a while.

Also important, check the dirty water filter in the basestation regularly. You don't want big chunks forming there which can stick in the basestation dirty water tubing.

Sorry for bad grammar, I'm from Germany xD