what is your goal? Are you planning on moving to a different city and employeer every year, or just want to settle down in aspecific place?
there are lots of jobs. However some places have specifit needs. Some jobs can be worked remote from anywhere. Some jobs depend on word of mouth so you can’t move after getting the skills.
The duolingo format was never popular with polyglots. The game format makes it easy to feel like you did something which is a great thing, but the is the only pro people who have learned multiple languages find with it.
There is a lot of debate about what the best way to start is, but all agree that you need to interact with the real language in real world type settings (watching a movie in the language with subtitles is real world, though you need to make an effort to listen not just read!) They also agree that time is important, you need to study at least an hour every day to make progress.