What are the best solutions to add payment options on my website (e-cards selling) securely?

I think Paypal might be a good idea but I'm afraid if they'll take all the money after sells (since it's e-cards, it's not expensive so I'd like to still get a good income).

Please clarify this for me and give me tips :) Since I'm 16, double thanks if you please show me how to do a business legally (I have a german bank account + paypal account), thanks :)

Concerning the code I'm not doing bad but I think payments must be taken very seriously!

Have a nice day! :)