1. A system for a vehicle, comprising: a head-up display; and a circuit, which is connected to the head-up display, wherein the head-up display is configured to project an image onto a front windshield of the vehicle or onto a separate combiner, wherein the circuit is configured to output image data to the head-up display in order to generate the image, whereby the image data have a set of objects which include messages for the user, wherein the circuit is configured to determine a user's workload level, based on a set of driving conditions, wherein the circuit is configured, based on the level, to switch between at least one first workload mode and a second workload mode, whereby the second workload mode is assigned a higher level than the first workload mode, and wherein the circuit is configured in the second workload mode to reduce at least one object, which is output in the first workload mode.