If you want to become fluent in French, you have to practice speaking it every day.
Only able to do two days a week?
That's fine. So long as you accept that it will take you much longer to become fluent. If at all.
The same goes for any other language, musical instrument, or skill you want to build.
The person who spends some time with it every day will always become more fluent than the one who dabbles a couple days a week.
Every, single time.