If you want to refresh yourself on the original before checking out the sequel, you have plenty of options.
Top Gun: Maverick' enemy explained: Who are they fighting? - Los Angeles Times
Top Gun (1986) - IMDb
Kenny Loggins' 'Danger Zone' Will Appear in 'Top Gun: Maverick
Twenty One Pilots say Tom Cruise fired them from Top Gun Maverick
Kenny Loggins recorded a new, unused Danger Zone for Top Gun: Maverick
Top Gun (1986) - Filmaffinity
Box Office: 'Top Gun: Maverick' Becoming Tom Cruise Top Grossing Movie
Flight of the Intruder (1991) - News - IMDb
How to watch 1986 'Top Gun' movie with original cast - Los Angeles Times