Since it’s abundantly clear that you’ve never actually read the 1st amendment, let me help you out:
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
As you can see, employment disputes are not part of the 1st amendment. As you can also see, it restricts establishing a state religion, exercising your religion, protects you from prosecution when peacefully assembling and when you are giving the government the finger.
I suggest reading through the Constitution and it’s amendments. It’s not a long read.