I don’t know what to write in English.

I want to write something every day, but I don’t know what to write in English. In Japanese I don’t have a ‘what shall I write’ stage.Is this the difference between ‘mother tongue’ and ‘foreign language’?

I honestly don’t need to speak English fluently for my life now. I just want to read and write. I myself need to read and write. And I know I need to speak it for that.