Hey again,
I got a slightly more complex work-around by creating 2 floats that control the pitch of the object. This solution is not optimal, unless you restrict the player to only be able to rotate the object by 90 degrees. As it is right now you could press the F button at any time (even while the object still rotating) and it would add 90 degrees onto the pitch as it is at that current point in time.
To prevent this you can add a simple boolean at the start, which checks if the object is being rotated. For that simply set the boolean to true once the timeline starts playing and then set it to false when the timeline is finished.
EDIT: resetting the pitch once it reaches 360 is also optional. You can have the pitch set to 720 or even higher and it would still work fine, however it would eventually reach a ridiculously high number and I am not sure if this could cause issues (therefore I decided to reset it).