"After nine unfortunate years, Žofie stopped trying."

[dsarkarati]

Why would this not be correct? "Po devíti nešťastných letech Žofie se přestala snažit.

[VladaFu]

second position for se

[dsarkarati]

In this sentence, "Po devíti nešťastných letech Žofie se přestala snažit.", "se" is in the second position in the independent clause. Can't the phrase "Po devíti nešťastných letech" be a unit by itself that doesn't affect the independent clause in which "se" is in the second position?
Would this alternative sentence be correct? "Žofie se přestala snažit po devíti nešťastných letech."

[VladaFu]

It isn't. The first unit of meaning is "Po devíti nešťastných letech", then is the second position and "se" has to come there. There are no independent clauses here, it is all one clause.

The alternative is correct.