The 26-year-old joined after cancelling his contract at Old Trafford and was presented to Brazilian media Tuesday night.
He said: "Do you think I'm not fit? A player will always be criticised. I had injuries in the past, but I have to be quiet right now and answer in the field.
"I had a knee injury and returned to play too fast. I played, but the knees where not equal and I got myself injured again.
"It will be a pleasure play in a club such Internacional. I want to be happy as I was in other clubs.
"I'm coming back to Porto Alegre because Inter went after me. The president gave me attention. I was training but not playing.
"I played for eight years for Manchester. I would like to thank the club. In my first four years I won everything."
Anderson added: "I would like to win titles here.
"I'm only 26, I would like to play again for the national team.
"I want to be that fast player that passes through two or three players. I'm still young and have played with great players. I have played just for top clubs, so I still have the ambition to play in Europe again. But for now, I decided to come back home. I have been a winner here before."
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