You can get grammar checker tools to correct your English sentences, or have English native speakers from various language learning platforms and language exchange sites and mobile apps to help you. You can ask for help with correcting sentences on English grammar forums.
Ginger, OnlineCorrection and Grammarly are three good online grammar checker tools. Ginger and OnlineCorrections offer instant corrections on their websites. Copy the sentence you need correcting into the provided box, submit it, and the tools will tell you if there are any mistakes and how to correct the mistakes. Grammarly requires you to register for an account, either free or paid. Then you can copy and paste your text into the Grammarly working panel. You can also upload documents from your computer.
You can often get help from English native speakers on language learning platforms, such as Livemocha or Lang-8. Register for an account, earn points and redeem them to ask for help with correcting sentences.
Language exchange sites and apps are other good sources to get help from English native speakers if you can speak another language fluently. You pair with one or more language partners who want to learn that language. In return, you can ask your partners to correct your sentences in English. Good sites are MyLanguageExchange and Interpals, while good apps are HelloTalk and Tandem.
Grammarly and StackExchange are English grammar forums where you can ask others to correct any sentences.