Using both the combined pill and external condoms is a great way to prevent both pregnancy and STI's - together they have a very high effectiveness rate.
You should be able to find them in pharmacies and supermarkets, possibly even free at your doctors surgery or from local youth services. In terms of brands, it's mostly a case of personal preference - which means trying a bunch out and seeing what you like! Some things to think about:
- Latex or non-latex?
Latex is most common, though it's not suitable for folks with a latex allergy, and some people like non-latex ones more for the feel of them
- What size?
condoms come in pretty standard lengths, but the girth can vary and should suit your partner's penis. If they're slipping, go smaller, if they're hard to get on and are splitting go bigger.
- What thickness?
a lot of manufacturers do thicker condoms marketed as "extra safe". In reality, these don't fail any less than the extra-thin ones since they tend to cause more friction.
There are safety standards for condoms worldwide, of which one of the most common ins the European CE mark (you can see logos for a couple of the recognised safety standards here: https://menrus.co.uk/sti-content/condom-standards/
). I would expect it to be pretty hard to find any condoms that DON'T meet one of the standards in Austria but it's nice to have that reassurance.