Hi Christian. If you're looking for a long-term solution, you can try hair transplant surgery. This involves the grafting of individual hair plugs on areas with baldness. These transplanted hairs are permanent.
However, most people prefer to wait a few years until their baldness is more significant before they have surgery - which is understandable since hair transplants are expensive and not something that should be rushed into. Here's an article about toupees that might be helpful if you both understand the risks and want to wear one for many years to come:
"Toupee vs Hair Piece". It