Why do I forget 60% of the words I "know" in a language

I consume french media and I understand a good amount of what is said. But when I have to speak in my daily life almost all the vocabulary I understand from the media is gone and I'm stuck with limited vocab. It's not just in french either, it's the same with English but to a lesser degree. Even my mother tongue but I don't consume media in that language anymore. Does anyone have any idea how to remember that vocabulary?

Edit: Thank you for all of your input I never knew about passive vocab until now. I'm going to journal and use new words I hear or learn whenever I can. I can speak to a french native since I am living in France and I have to know English for my course in uni so having a conversation is thankfully possible too. Thank you once again y'all!