To be honest, you probably never can. If you don't start as a child, you will probably never be perfect. Even people that have lived in an English-speaking country for years as an adult still make mistakes. But why do you need to be perfect? Generally, you just need to be good enough to be understood. To do that - you just need to practise.

By paying attention to corrections: "How can I learn English perfectly?"

The aim is to be able to be understood, Most English natives do not speak perfect English. In fact perfect English sounds archaic and cumbersome. You're better off speaking with a native speaker and learning colloquial English. Each region has their own accent and slag, which is sometimes difficult for a native speaker from another region to understand. I sympathise with people learning English!