It happens sometimes but, luckily, German is one of those languages which sound the way is written as well as Portuguese (I'm Brazilian). There were times I had to type new words and I got it correct :)
Anyway I agree with you. We have to read them first. Learning a language like English for example would be a struggle.
I looked for their difference and: " For the noun referring to articles, especially of gold, silver, or precious stones, used for personal adornment, jewelry is the preferred spelling in American English. Jewellery is preferred in varieties of English from outside North America." So I'll report this and hopefully we'll be able to use both soon.