Spoken French - improving quickly

Once you have mastered the basics, only practice can perfect your language. Immersion is very effective, but time consuming. If you have the time, an internship or something similar in a French-speaking workplace in your field could be just the ticket.

Failing that, I'd suggest carefully reading/watching/listening to everything you can get your hands on about your field in French. This will at least begin to build your work-related vocabulary, especially if you systematically note new words.

Then you need to turn this new passive vocabulary into active vocabulary, quite difficult unless you have the opportunity to use it. Perhaps you could find someone with whom to discuss your work in French. Have lunch with a French-speaking colleague, attend relevant lectures in French (and participate actively in the Q&A), participate in professional events in French , etc.

Good luck.