@Rubén16
I've only once offered a guest a refund for something like this and that was simply that the WiFi was erratic for part of their stay (after that I switched provider and it has been perfect). They were so very grateful, but I thought it was fair. Bad WiFi is super annoying for most people.
I have given other discounts and refunds, but it's not really been for something going wrong. E.g. my listing states that I do not store luggage, but some guests who had an insane amount (six suitcases and four carry ons for two people) asked if they could leave it here for the day and would pay. They left me a £20 note. I refunded them £8 for no reason really (they would have paid more at a luggage storage facility) but they were nice people and as I had no new guests checking in until the next day, it was not a big hassle for me. They were very grateful and mentioned it in their review.
I have also had long-term guests who fed my cats while I was away on a short work trip. They were happy to do this because they really loved the cats, but I refunded them some money from their stay as a thank you. I think this is a nice gesture.
However, if guests have some kind of problem outside of my property that is totally beyond my control, I don't think I am responsible to financially compensate them for it.