[torstenvl]

I'm a native English speaker but have a linguistics degree and have been a tutor. My mental model is that there are three broad things you need.

Knowing what it's supposed to sound like: for this I recommend radio and TV. This will help with aural comprehension as well.

Knowing how to make the sounds: for this, learning the IPA and looking at IPA pronunciation guides is very useful.

Putting it into practice: Find a native speaker who is learning your native language. Get coffee once a week. Speak English half the time and your native language half the time. If you can't make that work, try dictating to your phone/computer in English. If your pronunciation is good, you'll get better accuracy. Gamify it for yourself if you can.