How can I change a passive vocabulary to an active one? A passive vocabulary is a word that I know it when I see it in a text but when I want to speak, I do not remember it for using.
That really depends on how you and your brain works. Some tips that I'd suggest are:
Learning the translation both ways
Creating sample sentences with the vocabulary
Just practice and Practice
Find a way to write daily short texts about subjects you are interested in. At first you will have a lot of problems. But you will improve. By writing short texts you activate your vocabulary. Of course, you will have to look up a lot of words.