If you want to experience fast results you can try this exercise (after doing it you'll definitely hear whatever it is better than the first time around but there's still no guarantee you'll understand it 100%). People recommend using VLC player for adjusting the playback speed.
https://www.reddit.com/r/languagelearni ... ench_help/
copy paste from reddit
I devised another method, much less involved, here's the rough outline.
1. Read the transcript to a podcast/GLOSS-lesson/anything else really, write down all new words on paper and translate them
2. Read along as you listen to the audio
3. Slow the audio down to 80% speed and listen to it with your eyes closed
4. Speed it up to 120% and read along while it plays
5. Slow it down to 90% and listen eyes closed
6. Speed it up to 150% and read along
7. Listen to it eyes closed at normal speed, at this point you should understand almost everything