All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, is His slave and Messenger.
It seems that your question stems from Waswasah (satanic whisperings), just like many of your previous questions. Therefore, we advise you to ignore such whisperings and pay no attention to them at all; giving them attention corrupts the Muslim’s mind and religiosity.
All the things you asked about are lawful and completely free from problematic aspects.
Moreover, there is no need to research whether the Companions used to practice fish farming or not; this falls into the category of intellectual luxury and is dispraised as it is delving into undue details.
You should also know that there is no relation between eating green bananas (plantains) and what is reported in the Sunnah about the prohibition of selling fruits before they are evidently ripe. Green bananas are edible; how could you imagine that they are not in good condition or unripe?
Moreover, selling fruits before they are obviously ripe, provided that they are immediately cut off from the trees, is something permissible according to the consensus of the scholars.
With regard to the question about gold, we said in our answer to one of your previous questions that selling gold is permissible according to the unanimous scholarly opinion and that the possibility of using it in a prohibited manner does not affect the permissibility of selling it. Accordingly, it does not affect the permissibility of the project you mentioned.
Allah Knows best.