Camera zoom while walking

Hello, what i’m trying to acchieve is to lerp the “Target Arm Length” of CameraBoom item, increasing it’s value when character moves backward and decrease it when character moves forward. It’s needed because player will not be able to rotete the camera (it’s always lookin forward). But for some reason i just cannot make it lerp while the W/S keys are pressed, buyt it’s moving as i like when i release the key. Can anyone point me at the mistake?

Here some images from the blueprint:

P.S.
There is another problem, for some reason my timelines are animating for 2 seconds, no matter what i have set at it’s Length at the curve editor.

Didnt want just to wait for an answewr, so here it is:

im my previvous blueprint, untin W or S key was pressed i have called the “PlayFromStart” method of the timeline node. so i have added some nice branches and it’s working like a charm. here is the working blueprint if someone needs it: