Is it permissible to work in Forex, while believing it to be unlawful, in order to obtain a certain amount for studying aviation, and then leave it, knowing that there are Hadiths such as: "Every body that is nourished by unlawful earnings, the Fire is more befitting for it"?

Hesitation in abandoning what is believed to be unlawful is not permissible. One must accustom oneself to forsaking what Allah has forbidden, for the pleasures of this world are fleeting, and the Hereafter is better and everlasting. Whoever obeys Allah by abandoning what their soul desires has done well, and Allah will not abandon them; He will reward them generously in this world and the Hereafter. Do not engage in Forex trading due to the religious prohibitions it entails. What is described as Islamic within it is insufficient unless Sharia-compliant regulations are met, which is difficult to achieve. The intention to donate ill-gotten gains does not absolve the owner of sin. The search for quick profit methods is fraught with risks, and no one profits except at the expense of another. Goodness may lie in staying away from this work.