How can I make the animation to be loop without starting from the first frame but from the last frame? When the animation start the point light is at the bottom in the middle on frame 1 :

Then when it's getting to frame 120 the point light is on the left side but when it's starting over from frame 1 it's like jumping backward to frame 1 and start from there and I want it to continue nonstop and not to move backward but to continue from frame 120. Like endless animation loop.
Your question is not clear, do you want the object to come back to the center or do you want it to continue further to the left after frame 120 ?
For the first case, see Vklidu's answer.
If you want the object to continue further and indefinitely to the left, go in the Dopesheet press ShiftE &gt; Linear Extrapolation (or Channel menu &gt; Extrapolation mode &gt; Linear Extrapolation)