Haris Lamboo Faisal, ditto everything Mook Jong Man said plus:
First off, the drill I gave you is not to be used in the manner in which you are using it in this last video. So stop. The drill is the first part to a two part drill which only helps you learn to push the tan sao with the elbow, by sliding it when it makes contact to an opponent. Tan sao is not designed to bump or thump, but disperse by sliding and torqueing. Tan sao means dispersing hand, so like an arrow travelling through the air or a torpedo travelling through the water, it disperses an obstruction (an opponent's punch or blocking arm) out of it's way as it travels forward.
Second, again you are going way too fast in doing the drill.
Third, upon watching your tan sao in the last video, it also tells me you are doing your chain punching wrong, meaning you're executing the punches in a circular manner. Your punch and tan sao should come from the wu sao position straight out and not circle over the other arm, and the retracting arm should make a half circle or semi-circular return to the wu sau or elbow guard position.
Do the drill I gave you again, with the corrections discussed in previous posts, plus what I have told you here. But don't use a partner in conjunction with it YET!
Then produce a video of it and if it looks correct, I'll give you the second part of the drill.