"I am just an employee."
Translation:Jestem tylko pracownikiem.
It's like being 'just an employee', not 'just being an employee'.
"Tylko jestem pracownikiem" would sound quite weird, like it was the only thing that could be said about you.
Leaving the pronoun and saying "Ja tylko jestem pracownikiem" sounds okayish, but I don't know if it's worth accepting.