Listen to Natives, Speak More yourself

Usually people aquire them by listening to a ton of audio with people speaking in those accents. The best thing in my opinion would be listening to an audio book and then trying to read it out loud with the same accent. BTW if this was helpful feel free to check out my teacher profile.

In my opinion, the best way to brush up your pronunciation is imitation of native speakers. I would recommend this website https://breakingnewsenglish.com for listening practice. There are British and American accents, you can listen to different news stories at different speed. It is really helpful!