Is it permissible to engage in long-term banking transactions on the Moroccan stock exchange, where the deposited value is not lost and is invested in profitable deals weekly?

Dealing through the stock exchange involves many prohibitions. Your statement that the value deposited in the stock exchange never loses, if it implies that it is invested with usurious interest, then that is a sin. However, if you mean that those in charge of the stock exchange have expertise that enables them to avoid unprofitable deals, then there is no objection to investing with them if the conditions for validity in their transactions are met and they avoid prohibitions. Nothing equals safety, and whoever fears Allah, He will provide for him from where he does not expect.