Page 6: "They are my sworn enemies since they stole
my Razel heart"
Here, Razel's name was used in a possessive form; it should have been followed by an apostrophe and s-- "Razel's". I don't know what the raw ended the sentence with, so you'd have to either go by that or eyeball it if the original Japanese did not employ ending punctuation. (For example, a period or ellipsis ("...") followed by an exclamation point to signify an intensely emotional statement without actual shouting.)
Page 12: "Please feel free to call me"
The grammar isn't wrong here, but I'd like to offer food for thought, here. What Lana's saying doesn't appear to match the context (i.e., she's trying to establish casual friendship with Reifelt). The word "call", in English, has multiple meanings--generally surrounding the act of summoning someone. Used as shown on this page, it looks as if Lana's saying exactly that--but that wouldn't make sense. (For example, "call her" for what?) I went over the raw to see what she said, and it's as follows:
「気軽」, used here and in this context (as she just told Reifelt not to mind her status as second princess), means "carefree" or "lighthearted". 「声をかける」, as used here, can either mean to simply greet someone or to invite/get in touch with that person. It's not impossible that Lana was inviting Reifelt to call on her whenever Reifelt wants to, but does that sound like an invitation to casual friendship or the granting of a favor--especially when they are, in this greeting, establishing the details of their relationship? Lana also invited Razel to call her by name only two pages before. Therefore, you can conclude that Lana is actually inviting Reifelt to treat her casually--like a friend--rather than simply call her.
(If anyone else sees error in my analysis, feel free to correct me--I make no claims to JP mastery, here.)
With JP>EN translation, direct translation is a futile effort: there's bound to be loss of meaning or the application of an incorrect meaning in such a case, as there are many expressions in English that do not have a Japanese counterpart or vice-versa--but that doesn't mean that the meanings behind those expressions can't be communicated. Therefore, one must give thought to dialogue in the original language and not only see what is said, but also discern what's actually meant--and find a way to express that meaning in the target language.
Page 13: "I would be happy if Rifanel-sama would be friend with me from now on"
The word "friend" should use the plural spelling "friends", in that construction--referring to the two of them as friends. If she were to use the singular "friend", then she'd have to be asking Rifanel to be hers (i.e, "I would be happy if Rifanel-sama would be my friend.")
Page 15: "You are nothing more than a replacement until i return"
The pronoun "I" wasn't capitalized, here. In this usage, it always is. Japanese is a language that has no capitalization rules, therefore it's not an issue where usage of the language is concerned; however, to keep that mindset while translating into English--which has clear capitalization rules--will create grammatical errors and potentially lead to a lacking in clarity.
Page 17: "having no talent...or special qualities...is it really so bad to have that?"
The first word of any sentence, normally, should be capitalized--and "having" was not. Also, the text of that panel's second dialogue box was awkwardly worded--consider instead, "is that truly so wrong?"
Page 18: "but you who now insults your own younger sister"
This was the beginning of a sentence--"but" should have been capitalized. Also, "insults" is incorrect here, as it's used in a second-person construction--that is, it's a verb used with the addressed person as the subject. "Insult" is proper, here. (For comparison: first person is "I insult", second person is "you insult", and third person is "he/she insults". In a plural sense, the verb's normally in singular form--"they insult". )
Page 18: "is inferior to adventurers"
This continued from a previous sentence, and illustrates a potential pitfall of not using ending punctuation. Japanese, as I said before and naturally, uses different grammatical rules from English; while I do not know for sure whether or not it is grammatically correct, you often find a lack of period usage in casual JP conversation online. This is also the case with manga, as you can see in the raws. Similarly, Western comics have omitted final periods in dialogue as well, but not
all final punctuation. Here, Razel's words weren't final--they were to be followed up by a final declaration of Hana's poor character, which was shown in the raws by a long dash; that should have been included here.
That said, you omitted final periods in many sentences over the course of this chapter--which is normal, as said, for Western AND Japanese comics--but included them in some places in the beginning. You should be consistent in this regard--choose only one way or the other--but I strongly recommend using proper punctuation at all times, for clarity. Japanese is a language of omission; speakers leave out details that are readily assumed by those spoken to; this applies to their written word--and their punctuation as well, evidently. One might be able to do this in Japanese, but it will be much harder to get away with in English because of its rules. This will require close analysis (as I said before) of dialogue, but translation is not a brainless effort--not if you mean to do a good job, that is. I am sure you do, since you're asking for correction/guidance.
Page 21: "haha..."
Even if it's just one word, it still--normally--requires capitalization.
Page 21: "Are you okay? Razel-sama"
The question mark of such a construction in which the person being question is named after the question is posed should be final: "Are you okay, Razel-sama?!" Since Lana was distraughtly worried for Razel's safety, and Lana's question was exclaimed, follow the question mark with an exclamation point accordingly. (I.e., "?!") Or, perhaps, this construction: "Razel-sama! Are you okay?!" The second would illustrate her shock at the preceding event well via the exclamation of Razel's name.
Page 22: "I don't know anything about"
This sentence is missing the object--about
what? Rather, Hana was dismissively feigning ignorance of Lana's accusation. Consider instead, "I don't know what you're talking about."
Page 22: "Well, it's fine...more importantly"
This is a combination of three things I warned about previously: the pitfalls of not using proper punctuation, the difference in capitalization rules between Japanese and English, and attempting to translate Japanese directly to English. As is, it's readable--one can tell what she's saying and what's meant without trouble. However, it does not follow proper conventions of English, and--read as is--lacks clarity. Worded as it is, Hana is saying that her dismissal ("Well, it's fine...") of Lana's concerns were "more important", because those words were not marked as the beginning of a new sentence via capitalization.
Hana's words should have been rendered thus: "Well, it's fine. More importantly..." The reason for this is that those two last words were actually the beginning of the following sentence in the next panel.
Page 22: "You woman with slanted eyes over there!"
Since this is the second part of the sentence begun in the previous panel, it should have begun with an ellipsis ("...") and a capitalized first word: "...You, woman with slanted eyes over there!" The comma comes after "You" because she's addressing Rifanel with "you" and specifying her afterward--rather than just describing her as a woman with slanted eyes in a certain direction.
Page 22: "Don't think this will end like this!"
Readable--once again, everyone can figure out what Hana is saying--but it's unclear due to repetition: instead, and if you would follow the original Japanese that closely, consider "Don't think this will end like that!" "This" refers to Hana's conflict with Rifanel, and "that" refers to what Rifanel said to begin that conflict.
Page 23: "Oh, I just stating facts"
"I'm" is what you should have used there.
Page 27: "Yes, it's not allowed."
This is a direct translation of what Rifanel said in the raw; in Japanese, it works--but not in English. As you worded it, Rifanel expresses an affirmative but follows with a negative statement, creating ambiguity. To keep Rifanel's agreement with Reifelt while expressing the negative sentiment she agrees with, consider "That's right" (which is one of the definitions of 「ええ」) or something similar instead. (This is also to keep the apparent verbal gag: Reifelt and Rifanel were using the same words to express their jealousy.)
Page 27: "Cheating or anything like that, we're family, you know"
Once again--readable, but still rough. (Running short on time, so I'll have to be quick.) Consider this: "Cheating or anything like that--we're family, you know."