My car was taken by police after my friend got arrested in it. They. Are keeping it until they talk to me. Can they keep it till Friday if I need

If the car is evidence of a crime they have broad discretion in holding the vehicle until the criminal matter is resolved.  Most times they don't want the headache of keeping a car as they are expensive.  The officer may want to talk to you to assess whether you were culpable or not.  It may make sense in your situation to have an attorney call the officer and figure out what needs to be done to release the vehicle.  Many times an attorney intervening accelerates the process.  But again if they are holding the vehicle as evidence it is their discretion. The answer to the question of can they hold it is generally yes.