I'm a native speaking german and learned english in school. So I will probably never be writing and speaking english on the same level as a native speaker or as I do in german. That's why I write in german. I wrote some stories and published them myself for free reading on my website. Now I think, if I should translate them myself into english, to gain a bigger audience? Is that a good idea, or would my terrible english actually a downside and I should stay with german?
Stick with what you know. If your English isn't fluent, you're most likely going to annoy more readers than you attract. This is why when a publishing house puts out a book in another language they hire a professional to do it instead of having the author try and do it. Translation can be confusing and there aren't always words that translate accurately, so it takes someone who knows both languages in and out to do accurate translations. So I would recommend sticking to German since that's the language you're fluent in.