I know someone who had a student insurance with Mawista. They paid as stated in the contract. They offer a lot of different insurances so ymmv but for the 50€ a month student insurance they delivered as expected. It helped tremendously to tell the doctors what kind of insurance was used so they could consider it when writing the bill. Payment was usually within two to three weeks. So if you Hand in the bill to the insurance quickly you will usually get the money quick enough to pay the bills without using much of your own money. As with any private insurance you should have some spare money to pay bills that they have not covered yet though. I can’t say anything about ambulances or hospital visits though.