Is depositing money in banks forbidden, especially since one scholar permitted it based on the premise that the state stands behind these banks and no bank loses, and that the questioner has no experience with projects and is outside his homeland?

The ruling on depositing money in banks has been previously explained in the referenced fatwas. It makes no difference to the ruling whether the state backs these banks or not, nor whether a bank is losing money or not; all of that does not affect the ruling.