I am not sure what you mean by public English. Public or private it is the same. One difference would be formal vs slang.

Kind of like said above. You could watch TV shows, Movies, and Youtube would be a great place as well. You can find people to hold conversations with you in English and if you're saying anything that sounds off or you need help, they could fill in any gaps or answer questions. Just constantly try to find new words, learn grammar and just keep practicing!

watch english movies daily and have converstion with friends in english build vocobulay