There's a detailed summary at the link below, but here's the gist of each of the scenes you're missing:
Act 2, Scene 3: The Porter provides some light comic relief, and then morning comes and everyone discovers the body of Duncan. Macbeth reveals that he's killed both the porters at Duncan's door - whom Lady M was hoping to blame for the murder. Malcolm and Donalbain resort to escape, to England and Ireland respectively.
Act 2, Scene 4: A largely expositional scene that reveals that nature has gone haywire since the murder, and that Macbeth is to be crowned king at Scone. Macduff is going to Fife, and not going to the coronation. Duncan's sons, Malcolm and Donalbain are suspected of the murder.
Act 3, Scene 1: Banquo suspects Macbeth of having done some "foul play" to get the throne. Banquo goes off riding, and Macbeth orders two murderers to kill Banquo and Fleance.
Act 3, Scene 2: Lady M asks about Macbeth's plan to kill Banquo. He doesn't tell her. Their relationship is starting to crack.
Act 3, Scene 3: A mysterious third murderer joins the original two. The three murderers kill Banquo in the dark, but Fleance (his son) escapes.
Act 2, scene 3 Macduff finds the king dead and Macbeth kills Duncan's guards claiming that he acted in a loyal rage.
Act 2, scene 4 Malcolm and Donalbain are seen as responsible for their father King Duncan's death because they have fled (respectivily to England and Ireland) Macbeth is named King and his coronation is held in Scone. Macduff goes to Fife instead of Scone
Act 3, scene 1 Banquo thinks that Macbeth may be responsible for Duncan's murder, but refuses to say anything in hopes that his oracles will come true as well. Banquo goes riding with Fléance, his son, until the meal and promises to be back on time. Macbeth fears that his crown will be taken away soon, he feels that he must act imediately in order to keep it. Macbeth convinces 2 murderers that Banquo is their ennemy, they agree to kill him that day
Act 3, scene 2 Macbeth has a new found confidence and doesn't reveal his plan to kill Banquo to Lady Macbeth
Act 3, scene 3 Banquo is killed and Fléance manages to escape. There are now 3 murderers (3rd murderer is believed to be Macbeth but this is never truly revealed)
This is all that happened in Act 2
In act 2, scene 2
-Macbeth kills King Duncan
-Lady Macbeth insists of getting rid of all the blood and the bloody nightgowns they were wearing (to leave no trace behind)
-Someone is at the door
Act 2, scene 3
-Macduff and Lennox enter to wake the king and Macduff finds him dead
-Macbeth and Lennox go see for themselves and Macbeth kills Duncan's guards claiming that he acted in a loyal rage (althought it is seen that Macbeth kills the guards because he looses his cool and starts to panic in fear of someone discovering he was the one who killed Duncan) P.-S.: It is believed that the guards killed Duncan, which is a cover-up planed by Lady Macbeth and Macbeth)
-Lady Macbeth faints because she can't take the sight of the dead King Duncan (she is too frail)
-Malcolm and Donalbain decide to leave the country for their own protection
Act 2, scene 4
-Malcolm and Donalbain are seen as responsible for their father King Duncan's death because they have fled
-Macbeth is named King and has left for his coronation which will be held in Scone
-Macduff is going to Fife instead of going to Macbeth's coronation (unknown reason)