How did you improve your communication skill in second language?

Find someone online who wants to learn your native language, and talk with them for an hour a week split between the languages.

If you’re remote, use video so you can see expressions.

Tell each other how aggressively you want the other person to correct you. For example, if your speech is not what a native would use (it’s not “idiomatic”), do you want them to stop and tell you how they’d have said it? Or is your goal simply communicating your ideas clearly, even if it’s not native-level phrasing? These thresholds can change over time and based on the subject. For example, you might want to be native-level for conversations/topics that come up a lot, and simply good at communicating ideas (not native-level) for other topics.

To find these people, look at local cultural groups in both countries/cultures as well as r/LanguageLearning on Reddit. In Spanish it’s called an intercambio and you can Google for ‘intercambio directory spanish learning’. There’s probably equivalents for other languages. Worst case, you can pay for it through iTalki or Lingoda.

When you say speaking, I'm guessing that you're referring to conversational skills (which also includes listening and comprehension) rather than public speaking, which is often a problem even for native speakers.

Assuming that, I think the most important thing is total immersion. You'll need to spend a lot of time having conversations in English, preferably with native speakers. Depending on your circumstances that advice may or may not be easy to follow. For example if you're not very social or have family you converse with in your first language those can be obstacles.

The other thing to be aware of is that sometimes people have developed habits of speech or pronunciation that make their speech difficult to understand (or just sound strange) and they aren't aware of those habits. So you should also seek out some friends who are native English speakers and ask them to honestly evaluate your pronunciation.

I'm a native English speaker and that is how I learned to speak French at an acceptable level, after a number of years of living in France.

Practice. Use the language socially and casually. If you don't have an outlet for that, consider hiring a tutor. You're probably at the point where you want someone with some experience with more advanced (near-fluent) students. Do the entire lesson in English.

Something like a guided conversation where they move you through some topics in a structured discussion. Could be about English grammar, or the daily news, or some literature, or just popular culture. Whatever you like. They will ask questions about what you've been talking about, ask you to restate what they said, or ask questions about how you feel about the topic. Repeating this kind of exercise regularly can be very effective.

(And if your tutor doesn't correct your word choices and pronunciation almost constantly, you probably need a new tutor.)

I've always heard that it's helpful to watch TV and movies (and listen to the radio) in the language you're trying to learn. This gets you hearing the language in real conversations. (And maybe even repeat some of the sentences out loud, just for practice?)