My wife wants to improve her English.
It's a paid site to learn english
I wonder if there is any like that that is free?
This answer is more relevant to English Language Learners and indeed it's well answered with lots of resources in the Meta on that site: Resources for learning English. Some of the resources mentioned there are free.
The mechanics of migration and closing as a duplicate mean that leaving this question here as a signpost to ELL is worthwhile.