Movement

How can I do movement without the 3rd party program?

p.s. I'm talking about walking not jumping or looking up and down

Well, it's in the trigger repository I believe, something similar to this.

But the FPS way is that

1) Replace a model's any animation with the walk animation (because you can't call on the walk animation reliably).

2) Now, let's say you're doing an arrow key control, so when you press the up arrow key, the unit will move towards where it is facing, and when you release it it stops moving.

3) Now just implement it such that when you like press the up arrow key, instead of moving, you add to a certain variable. Let's say every second that the arrow key is pressed, Speed = Speed + 1. So we have acceleration. Then the guy just moves up by Speed squares per second.

4) To strafe left and right, it's just moving like in step 2 and 3, except this time it moves towards angle + 90 and angle - 90 for left and right.

If you want to put in things like terrain, slipping down slopes and stuff like in the FPS Mod, then just modify the FPS Mod map instead of creating a new map. It's easier that way.

Would it be possible to movebackwards without thirdparty programs?

Yes. The 3rd party only controls the input (pressing of keys and whatsnot). The actual moving is done in the map, so you just have to change the input.