It's really difficult for you to have no basic knowledge of French. Even if you have studied French before or your second degree is French, it will be much better.
I'm not attacking you, but stating the facts. Although people's subjective initiative can really exert great power, we should not ignore the present situation of the objective material world.
You are a junior now. Even if you practice hard day and night, the French pronunciation rules will take at least 3 to 5 months. Moreover, the reality is that many people can't overcome their pronunciation habits when learning English, which leads to poor French pronunciation. Fluency or not, if their pronunciation is not accurate, that's bad. Don't forget that if you take the French department, there will be an interview. The interview must be in French.
Next, let's talk about French words and grammar. After overcoming the obstacles in the phonetic stage, you will be the first to come into contact with them. French is notoriously difficult to get started. Words are divided into yin and yang, verbs into tense and person, and so on. These are the most basic and difficult parts, especially grammar.
Only when the grammar has passed and the words have accumulated enough can French writing become professional. You know, French students spend a lot of energy practicing writing. At the same time, there is listening. The biggest difference between French and English is that there are couplets when speaking, which will greatly hinder the judgment ability of listeners, especially those who listen less.
I have to remind you that the advantage of French majors over ordinary self-learners lies in that some of them have communicated abroad, or even those who have not, have received education in French literature, history and linguistics at home. The French version of literary works must be read more than ordinary students. If you want to make rapid progress in learning a language, you must understand the culture and social concepts of other countries. Culture takes time to accumulate, and you can accumulate more literacy. You are still a junior, and your undergraduate study of marketing is not over yet. You have a graduation thesis and internship in your senior year, so I'm afraid you can't devote yourself to learning French. In my opinion, French emphasizes professionalism and practicality (it does not rule out that some people like its literariness). If you spend a lot of time but can't get into the French department of a better university, then don't do it at all, because the French translation major and other related fields require fewer people but require proficiency.
From the perspective of postgraduate entrance examination, there are not many schools offering French majors, and there are few prestigious schools enrolling students. There are still some French students in our school who need to take the postgraduate entrance examination, not to mention those from the French department of other schools who took the cross-disciplinary examination. So I think your idea is good, but not practical.
If you like learning French, you can choose public subjects such as foreign languages and politics instead of taking the national entrance examination of English, and switch to other languages, such as French, which is a little less difficult. But law school really doesn't advise you to try. Since English is good, why not give full play to your own advantages? In fact, marketing needs people with good English ~
I hope you won't be discouraged by these words. As long as there is love, French can still be learned as a hobby.
I hope this helps you.