I became fluent by practicing the language. Reading is not enough. Writing is not enough. Memorizing is not enough.

I struggled to learn English until the day I started speaking it to get my thoughts across. I had gotten to the point of understanding most of the everyday conversations but it wasn't until I started speaking it that my fluency skyrocketed. I was easily speaking it within 6 months and was fluent within a year after.

So my suggestion to you, from a former mono-language speaker, is to start to speak the language ASAP. I know it's embarrassing but there is no other way.

Additionally, listen to audio and video programs with a dictionary in hand. Grammar and languages structure aids will help but by using them as your primary tools they will only slow your progress.

Duolingo is great simply because it keeps you going and it helps you practice but it's slow and you'll never be fluent.

Also, the reason most foreign language class teaching is ultimately a waste is that most people forget what they learn because they don't speak it as a way to communicate.

So, speak it, speak it...