Also the wallet I got "bither" is pretty confusing. I don't have a clue about api's or qr codes. I just want to buy around €500 worth of bitcoins, store them on a wallet I can actually understand and buy stuff, without all the technical stuff that goes along with it. Is that possible?
before doing anything else you should choose a good wallet for yourself https://bitcoin.org/en/choose-your-wallet
i have never even heard of "bither"!!! choose one that is popular and secure. and remember to always download it from the official website and not just a random probably phishing site.
for buying bitcoin i think your best choice can be coinbse.com which you can use as your wallet too but you have better and safer options.