"... over/under ...": In betting on sporting events, especially football, there are a number of derivative bets which can be made in addition to who will win and by how large a margin.
One such bet is called the over/under. A bookmaker will suggest that the total number of points that will be scored in a game will be, say, 32. You can bet either the over (more than 32 points will be scored) or the under (less than 32 will be scored).
"... Red Card ...": " I looked this up for you: If a goalkeeper is given a red card then he can be replaced by a substitute goalkeeper but a regular player has to leave the game. If the team is out of substitutions (3) then a regular player has to play in goal.