わたしはやまとです

ヤマト　大和  if you wanted to write your real name in Katakana, ザンダー ザビエル です。

わたしは，イギリスじんです。

そとはさむいです，（いま）日本では、or 日本は、そとはさむいですか？

sorry if my japanese is a bit bad i haven't had much time to practice and i have no one to learn it with:/

It's ok for your Japanese. I think it is the best way for learning if you are able to convey your intent. It is very difficult Japanese particle, isn't it? I also can't use them well in English also. keep up the good work. (^^)v