Since you're referring to a miraculous onigiri appearance in the past, use the 〜ました ending instead of the present/future 〜ます you have in there now.

I blame the dictionary's translation for not making it clear. ある日　indicates that the action has already happened, so the clause that follows it should be in past tense.　Therefore, you should use いつか which means sometime or one of these days. こんど works as well, but you can't have こんど and ある日 in the same sentence, that applies for こんど and いつか as well.

Good suggestion, I agree!

ある日　indicates that the action has already happened, so the clause that follows it should be in past tense.　Therefore, you should use いつか which means sometime or one of these days.

Thank you so much for the comments, I need practice to write japanese outside my private lessons.

I think you meant to write で instead of て、am I right?

Ｙｅａｈ、thanks a lot)

sorry, I'm an English teacher: miracle, not miricle ^.~

Thanks for catching that. I'm a terrible speller. lol

after speech clauses, you need to insert a と before 言います, and when you use ながら, the verb needs to be in the stem form - 私が「分かりません」といいながら，かれは。．．
Also, ぶとう is a noun, not a verb, so it can't be conjugated. You can do ぶとうする, but おどる (踊る）would probably be better. Lastly, ある日 is only used in the past tense, so instead of ある日，日本語をならいます, use something like いつか or こんど.
Good job with everything else though! This was a really complex sentence ^.^

You mi-spelled くに。

I don't think you need のうちに here

私を出かけて should be changed to 私は出かけて because "私" is the topic of the sentence, not the direct object. お化け物を現れりました should be お化け物が現れました. 現れる is an intransitive verb; therefore, it doesn't take を as its particle. Plus, it's an ichidan verb, so the ました form should be constructed by using the stem 現れ + ました = 現れました. Hope that helps.

私のパンツがどこだ?! should be marked with the particle は instead of が. パンツ is the topic of the question, while the location of パンツ is the subject of the question (omitted in this sentence). I hope that makes sense, but I don't think it does. If you want a further explanation, let me know.

Oops, sorry, that was a typo. >< It must be because g and h are right next to each other on the keyboard. XD I should have proofread before I sent it, lol. I do understand the difference between は and が and stuff and when I should use them, btw, so, you don't need to explain it. ^^