If you have supplementary insurance, you may ask your self if you need to be covered for all situations included in the package. For instance, you may be interested in coverage for physiotherapy, but the package you have may also cover contraceptives, glasses and alternative treatment, in which you are not particularly interested. Check if your insurance provider has a package that just covers physiotherapy.
You may also check if the premium you pay for the supplementary package is likely to save you costs. For instance a typical insurance for dental care will cost you 240 € per year and covers up to 500 € in cost. If you have strong teeth and just have 1 or 2 checks per year and maybe a simple filling, the charges you will incur are most likely less than your premium. At the same time, if you really face some serous dental work, 500 € won’t get you far.
So just check if in your case the potential benefits outweigh the premium. Of course, Dental insurance may very well be of value in your particular situation, for instance if you regularly have yearly dental costs that exceed the annual premium of if you have children that may need orthodontics as this often requires one of parents to have a dental package.