You know every word in the sentence and still cannot follow it. That is not a vocabulary problem. It is that written English and spoken English are joined together differently.

Words link into each other

When one word ends in a consonant and the next begins with a vowel, they merge:

  • "an apple" → "a-napple"
  • "pick it up" → "pi-ki-tup"
  • "turn it off" → "tur-ni-toff"

Small words shrink

Unstressed function words reduce almost to nothing:

  • "to" → "tuh"
  • "and" → "n" — "fish and chips" becomes "fish-n-chips"
  • "of" → "uh" — "a cup of tea" becomes "a cuppa tea"
  • "for" → "fer"

Some sounds vanish entirely

  • "next day" → "nex day"
  • "most common" → "mos common"
  • "I don't know" → "I dunno"

Sounds change when they meet

  • "did you" → "didja"
  • "want to" → "wanna"
  • "going to" → "gonna"
  • "got you" → "gotcha"

What to do about it

Two separate goals, and they need different work:

  1. To understand it — listen actively, transcribe short clips, and check your transcription against the real text. The gaps you find are exactly these reductions.
  2. To produce it — shadowing. Copy the rhythm, not the individual words.
You do not have to speak this way to be understood. But you do have to hear it, or fast English will stay a wall.

One caution

Do not force contractions into formal presentations to sound native. Clear, slightly slower speech is more effective in professional settings than imitated casual speech.