How to fix a faulty engine in the Audi A4?

I recently purchased an Audi A4 and have been experiencing engine troubles. The car's performance has decreased significantly and there are strange noises coming from the engine. What could be the cause and how can I fix it?

First, it's important to properly diagnose the issue. Take your car to a certified mechanic or dealership to assess the engine problem. They may recommend replacing certain components or performing maintenance on the engine. Depending on the issue, it could be fixed easily or may require more extensive repairs.