Question

What did hitler mean when he said "I wish to thank Him who allowed me to return to my homeland so that I could return it to my German reach "?

Answer 1

I interpret "Him" here to mean God (this is why it's written in a capital letter).
So, Hitler thanks God that it was possible for him to return to Austria- a country where he was born but where he hasn't lived in a long time- and by returning to Austria he joins Austria with Germany, which he believes it should always have been ('return").