There is a step wise progression you should aim at which will take you from one level to another if you are looking at getting proficient in learning French Language. Though,the number of weeks involved in clearing a particular level depends on your level of commitment but a fair estimate can be given based on statistics.
Lets start with French for beginners or the beginners level, where one can understand a few words and expressions only.
An Elementary level (Level A1*) at which the student has an understanding of simple sentences and instructions but is unable to form sentences with correct grammatical usage. (4 weeks)
Upper Elementary Level (Level A1-A2*) enables students to master speaking and writing example sentences but cannot understand daily usage language. (8 weeks)
Lower Intermediate Level (Level A2*) is one at which, the student would be making mistakes on a frequent basis but can express using various sentences without the precision in understanding the language. (12 weeks)
Intermediate Level (A2-B1*) ensures that the student would have a better general understanding of the French Language. However grammar, vocabulary and accentuation are areas which need to be worked upon still. (16 weeks)
Upper Intermediate Level (Level B1*) by which the student would have enough knowledge which is operational and can be applied professionally. A student is in a position to express ideas with a few shortcomings here and there. (20 weeks)
Advanced Level (Level B1-B2*) is one which confirms the mastery over French Language, oral as well as written. One can understand the language spoken by the native people and is capable of expressing in any situation confidently. (24 weeks)
Very Advanced Level (Level C1*) brings a student very close to the mother tongue even in not so simple situations. The frequency of errors is almost down to nothing. (30 weeks)
Proficiency Level (Level C1-C2*) makes the student completely proficient in French Language speaking and understanding and attains mastery on the subject. (36 weeks)
* Common European Framework Scale
Levels of French Learning