Is it permissible to open an account in a German bank according to a plan that saves money through investing in the shares of major companies, knowing that the value of shares may increase or decrease? And if the answer is no, is it permissible to adopt this plan on condition that the additional funds from the employer are returned when the amount is withdrawn?

It is not permissible to save money using the first method (bank deposit) because it is an interest-based deposit, and it is forbidden to engage in usury, even if the interest is disposed of, unless the money can be placed in a current account. As for the second plan (investing money in stocks), it is permissible to purchase pure shares of companies whose activities are permissible and do not deal in interest. It is not permissible to purchase mixed shares (whose activities are permissible but deal in interest) or forbidden shares (whose activities are forbidden). The purity of the shares must be verified before purchasing them.