Close combat timing
Timing in general is described in the chapter Fight timing .
In close combat (and in any other activity) you always have 2 base actions available.
Basic maneuvers
Every maneuver must include at least 1 base action.
Thanks to training you can have extra bonus actions, rarely even a base action (you can have it thanks to a premium from reflexes).
Some feats, however, may allow a maneuver without a base action, for a bonus action only.
If you have no more actions, you can attack only 1x and defend 1x in a round, or attack 2x, or defend 2x.
Be careful with your actions and save them for defense, otherwise you may end up defending passively!