There are many levels of learning a language from tourist level to discussion of complicated subjects. In a few weeks you may develop some of the basic skills but it takes years to get to a conversational level. How often you are able to use the language makes a big difference. If you are living where you can speak French full time, you will learn much faster than using it for a couple hours then going back to your native language. People that are self conscious tend to take longer to learn to speak a foreign language also.