Hi Eman,
I'm not sure how to help as I don't know your level or what you are watching but here are a few suggestions:
1. Make sure the videos are not too long, complex or challenging. Start with topics that you are familiar with already.
2. Watch the videos WITH subtitles first, note any new / challenging language, then watch without subtitles.
3. Improve your understanding of how English pronunciation in rapid speech affects how the words sound. For example, consonant-vowel linking, vowel intrusion, dropping sounds and so on all impact the way words sound and can make it challenging to understand rapid everyday speech.
Hope that helps!