How to play Knockin' on heaven's door by Bob Dylan

Tutorial (chords+strumming).
How to play Knockin' on heaven's door by Bob Dylan.
Oh my God, I won't never be able to pronunciate corectly "G". Lol

CHORDS:

G, D, Am, C

Strummmming is something like this:

On G and D: D DDU
On Am and C:D D UUD, DUDU or D D UUD DDU