After a lot of this forum help so finally I made my quadruped robot (for now still has two legs) walking!
(each legs ----> 3 servo motors for lateral and longitudinal leg movement + forearm vertical movement. In these videos lateral leg movement is disabled)
Here the medium speed walking:https://www.youtube.com/watch?v=JqQx0KzGuMY&feature=youtu.be
Here the full speed walking (it's almost running!)https://www.youtube.com/watch?v=QW_KstrySAI&feature=youtu.be
In the future it will have a lot of sensors in the feet to determine where the ground is and it will have a lot of distance sensors to track objects to avoid collisions and to follow a specific path.