The most common way to reduce a medical insurance premium is to voluntarily opt for a higher Franchise. In other words, you can reduce what is actually covered. By doing that, you would also be agreeing to bear a higher portion of the risk yourself.
The higher the Franchise (i.e. whether you pay the first Fr. 300 of medical costs out of your own pocket, per calendar year, or whether you pay the first Fr. 500 or the first Fr. 1'000), the lower the premium each month.
I think the decision criteria for opting for a higher risk are the same as what I posted over in your other thread:
Here, for example, is an advice centre run by the church in Basel (I think that's where you are)
I don't think you need to be a member or have any church/Christian affiliation to visit their advice centre, and I think (but you'd need to check) that it is free.
Als Einrichtungen der Kirchgemeinden bieten die Sozialdienste Einzelberatungen und individuelle Unterstützung an: Beratung und Betreuung bei persönlichen und familiären Schwierigkeiten, Krankheit und finanziellen Problemen. As institutions of the parishes, the social services offer individual advice and support: advice and support for personal and family difficulties, illness and financial problems.
Here's another advice centre (perhaps better for you) that is specifically for young people between the ages of 12 and 25.
http://www.jugendberatung-juarbasel.ch/
This one is definitely free. It offers confidential help, and advice about a range of areas of one's life, of which getting one's finances in order is one.
For both of them, you could mail or phone them and ask whether someone could help you in English.
By junking all the complimentary polices, have the maximum franchise (Chf 2'500.--) and maybe checking which canton you live in.
That works for a calendar year.
Starting each 1st January, the balance is re-set and again you will be responsible for the first Fr.2'500 medical bills of the year.