Firstly, as I'm sure you're aware, learning a language takes time. Since you already know French, learning German wouldn't be that difficult or as time consuming but it WILL take you a year or so and if you want to get an actual degree (which you will need for a job) it will take even more time and money.
Of course if you know two foreign languages your job opportunities will increase, be it as a translator or a teacher. Now you can get jobs that require either German or French - this alone should increase them twofold.
So right now you need to consider where you are in your life, financially as well as otherwise. If you think that you can afford to spend the time and money to learn another language for another 3-4 years and then get a job, then go ahead. This could potentially give you a more lucrative job offer than what you'd get now.
On the other hand, you can always get a job now, and with it the associated financial security, health benefits etc.
If you're still interested in learning the language for personal reasons, then go for it! In fact, this is probably the best solution, if you can manage to keep up with it-
Get a part-time job that utilises your French skills whilst learning German. This way, you're also earning money while you're still studying, which will be a great advantage later.
Or else you can enquire about part-time German courses that give certification. Most of these will have night-time classes available on weekdays or weekend only classes and you can learn German while having a full time 9-5 job.