Insides & tips for the right sun protection from our Dr. Lars Rüther, laboratory and research manager at Dermatest:

[+] Use at least SPF 15.
[+] Apply a sufficient amount; for the face at least half a teaspoon full.
[+] Avoid going out into the sun during the warmest hours of the day, wear sunglasses and/or a hat.
[+] Reapply after about 20 minutes in the water or if you sweat excessively, as only about 50% of the protection remains.
[+] It is better not to use a spray (aerosols are inhaled, uneven distribution).
[+] Choose products with a good UV filter and no irritating ingredients.
[+] It's best to use a sunscreen with antioxidants on your face, neck and hands, which really get the most sun rays.