Steffi Graf didn't participate at a German Tennis Championship until 1982 at the German Youngster Championship, not in 1979, as suggested in the movie.
The announcer at Wimbledon mentioned that 1991 is Agassis first appearance at the Wimbledon Champoinship. However Agassi also participated in 1987 at the Wimbledon "Men's Singles", which was his first appearance at the main draw, but he lost in the first round in Section 7 to Henri Leconte.
In 1991 Peter Graf tells Steffi that she is not Nr. 1 yet. However by that time Steffi did win first place at various Tennis Competitions, including the WTA-Finals in 1987 and 1989, Australian Open 1988, the Olympic Games Seoul 1988 including all Grand Slam Tournaments in 1988.
The logo of the French Open in State Roland Garros, Paris 1991, looked completely different that the one shown in the movie during the press conference.
The Training Arrangement between Andre Agassi and Nick Bollettieri ended in 1993 after Wimbledon, not in 1995, as suggested in the movie.
When Andre Agassi is driving through Las Vegas in 1995, the "Aria Resort & Casino" is visible. It didn't open until December 2009.
In the 1995 Scenes Andre Agassi is shown wearing his Long hair wig to Hide his falling out hair. In real life he was appearing with a shaved head already since 1994.
In the hotel Scene in London 1991 and later at Graf's home in 1995 a microphone of the German TV-Radio Station SWR is visible with the modern logo on it. Furthermore the SWR didn't exist until 1998, until then it was still separated in SWF and SDR.
When meeting Steffi Graf in London 1999 Andre Agassi said that he and Brooke Shields got divorced over a year ago. However their divorce was finalized in the very year, in 1999. However Agassi could have meant that they were separated over a year ago, which fits in the narrative of the movie.
Steffi Graf said Andre Agassi at Wimbeldon that she is having a Birthday. However Wimbeldon 1991 was from 24th June till 7th July while her Birthday was on the 14th June.