Learning with textbooks
Read and listen to the new lesson's text first (before looking at new vocabulary list and grammar explanation).
Conversations With Natives
Take conversational classes with native speakers or teachers before you can speak this language (from the first week). It's awkward and uncomfortable but this is exactly what you need. You need to put yourself in an uncomfortable situation where you can't use this language. It spikes up your Reticular Activation System (RAS) and turns on your subconscious mind.
Start massively exposing yourself to this language by watching videos and movies in this language, even if you don't understand anything.
2. Classes with Native Speakers from Day 1 (Using Selected Textbooks)
Take classes with native speakers and create a schedule around it. You can do it online very easily. Take at least 2 classes a week.
3. Use Speed Learning
You need to finish at least 2 to 3 textbooks to get to intermediate level in any language. But the good news is that you don't have to spend years on finishing them. The key is to finish 2-3 books in 2 months and relearn everything again during the 3d month.
When doing speed learning, it's important to understand one key concept: You don't have to remember everything but you must understand it. It doesn't matter that you forget all those words and grammar structures because the key to learning is forgetting.
However, it is absolutely crucial that you understand the grammar structures and word usages. You should practice grammatical structures by doing grammar exercises with every type of grammar.
It is important to underline that you need to be comfortable with forgetting and reviewing many times. You need to go through the loop of forget-review many times over many periods of weeks and months. That's why you need to review those books 2-3 times. But the good news is that you can do it during a few months while most of the people spend years on it.
In conclusion, if you want to have an elite-level fluency in any foreign language within a short period of time, you need to use tools and systems which are not used by most people.