Is it permissible for me to work as a computer engineer in an investment bank? And is it permissible for me to take money I inherited from my non-Muslim grandfather?

First, it is not permissible to work in a bank that operates on usury (riba), due to the assistance it provides in sin.

Second, if your disbelieving grandfather bequeathed money to you after his death, the will of a disbeliever to a Muslim is valid, and it is valid for one-third of his wealth or less. Anything exceeding that depends on the approval of the heirs. However, if the money is an inheritance according to the laws of the country, the majority of scholars hold that a Muslim does not inherit from a disbeliever.