I'm an assistant professor in a non-English country. I work in control system and signal processing. I write publications in my native language. But I want to get experience in publications in English. But I think my English is not so good. So I have small questions. Does anyone know courses or sites where I can practice? I know about Arxiv.org, but I am not sure it's best practice for my problem.
I am personally not aware of any open online courses although I would be surprised if none existed. I can, however, point you to some other good resources. First there is the Purdue Online Writing Lab (OWL) which has guides and resources for teaching so it is not a course in itself but contains very useful material. I can also recommend a couple of books on writing in English for non-native English writers.
The first is
Robert A. Day and Nancy Sakaduski, 2011. Scientific English. A guide for scientists and other professionals. (publisher link)
Hilary Glasman-Deal, 2010. Science Research Writing For Non-Native Speakers Of English: A Guide for Non-Native Speakers of English. Imperial College Press (link from publisher page)
and then of course
William Struk Jr and E.B. White, (many editions over the years). The Elements of Style. Longman/Pearon. (publisher link)
There are 2 approaches to learning academic writing in English and I'd recommend both of them.
The best way to learn the conventions for academic writing in your field (and it does vary between fields). You should read a lot of publications to gain familiarity of how to explain complex topics in your field. The more you read, the more confident you'll get with writing in English yourself.
You can also improve by getting feedback on your writing. It can be difficult if you are in a country where English is not the national language. Still you should be able to get friends and colleagues to give you supportive feedback. You can even get your students to contribute to papers and learn from each others English. Another option is to hire a proofreader to check one of your manuscripts. You can use any suggestions and edits as an opportunity to learn why it needs to be changed. Every time you get a proofreader to help you, you can improve on your writing skills.
Your writing does not have to perfect to submit articles to journals. As long as they can be understood in terms of the science, they can be reviewed. Minor issues with grammar and terminology can be sorted out during the review process. Reviewers should point out minor issues that need to specifically addressed, such as confusing or ambiguous sentences. These can be sorted out during revisions and resubmissions.