What should I do for Allah to accept my repentance and improve my condition, after I joined a club through bank installments, and recently discovered that this is forbidden?

If the partnership in question refers to an interest-bearing loan taken out due to ignorance of its prohibition, then there is no sin upon the borrower, and it is permissible to benefit from the money. This is based on Allah's saying: "So whoever receives an admonition from his Lord and stops, he may have what has passed, and his affair is to Allah" (Quran 2:275), and His saying: "And there is no blame upon you for that in which you have erred, but [only for] what your hearts intended. And ever is Allah Forgiving and Merciful" (Quran 33:5). The principal amount of the loan must be repaid without the usurious increase, if possible. There is no harm in benefiting from the club in which one is a partner, because the prohibition of the loan pertains to the liability of the one who takes it, not to the money itself. To overcome difficulties, it is recommended to supplicate frequently, renew repentance, and seek forgiveness.