Is the salary considered unlawful if one was employed by a company based on inaccurate information provided during job interviews, such as lying about the date of leaving the previous job and exaggerating achievements and tasks that were not performed?

If you are employed in this job and perform it as required, and you are competent in it, then your salary is lawful, provided that your work is permissible according to Sharia (definition). What you mentioned does not affect the lawfulness of the salary. However, it is incumbent upon you to repent from lying and to excel in your work.