Help with these phrases! please!
 

なんだ 僕のこの瞳がいけないんだなあ
nanda boku no kono hitomi ga ikenaindanaa

その中で見えたのは 見たくないような出来事
sono naka de mieta no wa mitakunai youna dekigoto

In the first phrase I have doubts with the "nanda" at the beginning and with the verb "ikenaindanaa" if I'm not mistaken -ndanaa it's form of saying but not sure what it means

in the second one I translated it like "inside there can be seen, it seems like I don't want to see it happen", but I'm pretty sure it is not like that

Please help me!!! I'm translating something and I want to keep doing it but these two things are stopping me for continuing

Thank you very much!!

If you wanted the best response possible, you should have provided more context, the whole piece that is to say.

なんだ here means "Oh, OK so ~~".

You should not separate the いけないんだなあ part from the preceding noun.
The phrase means "So it was my eyes that were causing the problem." or "It was my eyes that (someone) did not like". Hope you know by now what I meant by "provide more context". In Japanese, the same words/phrases have different meanings depending on the context they appear in.

The second phrase means:
"What I saw in there was an incident that I would not have wanted to see."

Finally, you do not need to write the romaji. These phrases are not something that romaji-users out there would understand, I asure you.

Ok thank you so much!
I still have a long way to go to finish what I'm translating, so if I have more questions I will provide more context, is the -ndanaa after the word that causes me problems, I don't know how it modifies the sentence
Thank you so much!

「んだ」 is the colloquial pronunciation of 「のだ」, which in this case expresses the speaker's affirmation of something based on reasons.
This is why I used "Oh, OK so ~~".

If you come to Japan and eat at Mac-D, you might say:
「日本のハンバーガーって小さいんだぁぁ。」
In order to sound natural, never fail to elongate the だ syllable if no other word follows it.

If another word follows the 「だ」　as in the first one of your original phrases, do not elongate it. Instead, elongate the very last sentence-ending particle. This is why that phrase had 「なあ」, and not the short「な」.

Ok, I understand now, thank you so much!!