Troubling Poem

I actually felt as though I understood the basic meaning of all the poems. The poem that did present the most difficulty to understand was "To his Coy Mistress". While reading it I grasped that this was in essence like a letter written to this man's mistress in which he professes his love. He starts out by explaining that they're love is everlasting and nothing can break it. Then Andre Marvell writes in his second stanza that while love is everlasting he can hear time passing and they should take advantage and not wait but I am very confused what the last stanza means and what meaning it has overall. Does anyone have any ideas? It seems like it's written in code and I don't know what he could mean by "Thus, though we cannot make our sun/Stand still, yet we will make him run "(ln 45-46)or "Now let us sport us while we may;/
And now, like am'rous birds of prey".