Hi, i hope someone can help me,
i tried everything, searched everything, can’t find a solution 
I hope my Image is self explanatory
sry for bad english.
Thanks!
I would probably create a variable called desiredRotation and set desiredRotation = 90 * X axis value.
I would create a function called setCameraRotation and call it every tick. This function would take in the delta time from the event tick.
In the setCameraRotation function I would use an FInterp node getting the cameras current relative rotation and break the struct to get the yaw float value. Using the FInterp to smoothly move from the current yaw value to the desired yaw value. Then I would make a rotator passing in the current pitch and roll while setting the yaw float to the Finterp result then set the relative rotation to that new rotator.
Hope that makes sense and share your result if it worked well or not.
-James