these lines are all from Act I, scene i
"I am too much i' the sun," Hamlet is pretty good with the English language. He says allot of stuff that are subtle jibes at Claudius. The "Sun" was considered a metaphor for King. Hamlet is saying that he is too much in the King's company as of late.
"Ay, madam, it is common," Gertrude has just finished lecturing Hamlet on the facts of life. She tries to tell him that his father's death was only a natural result of old age, "Thou know’st ’tis common. All that lives must die, passing through nature to eternity" Hamlet's sublime reply is that he knows that death is common. The subtext is more like "stop treating me like a child mother!"
"seems, madam? nay, it is. I know not 'seems" Gertrude has just asked why Hamlet seems more depressed than everybody else. Hamlet catches onto the word "seems" and throws it back at her. He says that "seems" infers that he is merely pretending to be sad when in fact it is the other way around. Everyone else is pretending and he is authentically in mourning.
When Hamlet says, "Ay madam, 'tis common...", he is calling his mother a whore.
"common, adj. and adv.". OED Online. December 2018. Oxford University Press. http://www.oed.com.jpllnet.sfsu.edu/view/Entry/37216?rskey=yq32zF&result=3 (accessed February 03, 2019). Cf. 6b.
