I have a text written in English (scientific). I want to ask somebody to give me some advice in writing and grammar. I have time to do the same for other persons in Spanish, my native language. Is there a site where I can "exchange" corrections?
Is there an online resource to exchange grammar corrections in one's native and target languages?
It sounds to me like you're describing Lang-8.com, which describes itself as "A new language learning platform where native speakers correct what you write."
Although I have not used this service, and their introductory video makes it sound like it might be for more casual writing than something scientific, so YMMV.
1iTalki does have this feature as well– OokerJul 4, 2016 at 11:16
I have used lang-8, it does work quite well. The basic idea is that you write blog posts in the language you are learning, and you correct other peoples blog posts written in your native language. There is a voting/rep system similar to the one in use here.– alzeeJul 9, 2016 at 16:21
I use lang-8, but it does tend to be for more casual writing than scientific stuff, so while of course there's no rule preventing you from posting scientific or technical writing, it may be harder to get feedback, because if people are not familiar with the subject matter, they will have difficulty knowing what you are talking about, so you will have people either saying, "I don't understand what that's about; I'll let somebody who knows about that topic correct it" or making corrections based on their best guess, in which case the accuracy of the corrections is questionable.– kristanAug 9, 2016 at 7:03
lang-8 is apparently shutting down Mar 10, 2017 at 8:38
The Tandem app on iPhone or the Hellotalk app on both Android and iPhone are two language exchange apps you may find useful.