you can change the speed of a frame by right clicking and then going to properties or just double left-clicking.
Thank you
Tried it and it works !
Anyway here's my edit:

something very important that your animation is missing is anticipation, unless he's doing a stab, which uses a very light weapon. you're gonna need anticipation frames to show that he's actually thrusting something heavy.
After the anticipation comes the actual thrust: To really "sell" the motion of the thrust, I added a smear frame.

After this one I have your original frame that shows the audience what is actually going on. I usually have this frame on a lower speed, which makes it give more impact.
For the last frame I added a small remainder of the shield(?) so it doesn't look like it's not immediately erased from existence.
If I were you, I would leave the tail from the animation, its very distracting and doesn't add any good secondary motion. If you really wanna keep it, at least make it shorter so it isn't as confusing.
Wow, thank you for the tipps!
It looks much better, a littlebit bouncy, but now I see what I'm missing. I wanted the second frame to be the anticipation, but I missed that totally I guess.
Btw., Valeera is a women with two daggers ^^
I tried to make a lightweight double swing motion.
The total motion I wanted to be:
- standing
- kneeing
- thrust forward ( this frame is missing as anticipation frame I guess )
- swing ( flashy lights
- step back
- REPEAT
Here is an original standing picture :

One more question, how long did it take you to make the changes

?
Just want to know how fast such things can be in the future to build ( at least in one year or so ^^ )