Is the salary a young man receives from his work in a shop that sells building materials, whose goods are imported illegally and whose owner bribes the police, permissible or impermissible? And is the extra money his employer gives him, beyond his salary, permissible or impermissible?

The ruling on your work and earnings in the shop depends on the lawfulness of the goods you sell. If they are permissible and free from deception, then there is no blame upon you. The sin of the shop owner importing goods through illegal means falls upon him, if the law is one that cannot be circumvented or evaded. A law that brings about clear public benefits or prevents harms must be adhered to, outwardly and inwardly. However, if there is no clear public benefit in it, then it is not obligatory to adhere to it inwardly. If his circumvention is to lift injustice and avert harm, such as evading unlawful taxes, then there is no sin upon him.