Spend time in...
Lessons are used to introduce new words, so this will be the starting point for you.
After some time of learning a language, you can try to translate sentences in the lessons before clicking on the translation. This way, you can strengthen your memory of the language’s vocabulary.
In lessons, words have different colors based on how familiar you are with each of them. However when a word is first introduced, you will notice that there is no background color for it and you should click it first to add it to your learning process.
Most people usually do not come back to the lesson they have completed. But it is a good strategy to revisit the lessons you have passed to see how much you remember. Besides, everybody knows that practice makes perfect.
How many new words is optimal?
The minimum number of new words you should learn daily is 10. But for optimal results, I suggest you learn 20 new words per day, or 30 words when you have more time. By doing this consistently, you will only need around 3 to 4 months to reach the higher level of B1 or B2.
In the beginning you need a smaller amount of lessons to reach that daily target number of new words; this is because every word is a new word. But as you learn more, the amount of lessons you need to complete the target number will increase.
If you are very optimistic, you can learn a maximum of 100 new words per day. However it is not advisable because reviewing many words may be hard.