Quite amazing ! You should change your Username to PrepaidGuru or so

Anyway, I have entered in my account and tried (with the help of Google translate) to find out my status. I think I understand what happend. I have activated data option XL and since it is not supported by the free prepaid plan, I got zero (well 0.01 Euro) credit.
By using MDMA, I've sent USSD for checking credit and got this message:
"Ihr Tchibo mobil Guthaben betr{gt: 0.01 Euro. Jetzt auch Ihr Guthabenkonto aufladen: einfach *103*Aufladenummer# und die H|rertaste eingeben."
I still have a couple of questions:
1. How can I make sure my above assumption is correct and I have not done another mistake (e.g. opening the comfort account, etc.) ?
2. Can I somehow top up my credit while in Israel (e.g. by using credit card) or the only way is to buy a voucher (Tchibo or O2) while landing in Germany ? Transferring money to Tchibo's bank account looks somewhat too complicated compared to the above.
3. Should I activate the data option again or am I sticked with the same option (I believe XL) for the rest of my life ?
Thnaks again for your generous assistance.