Hey Zizka,
I'm new to pixel art myself and I'm gearing up to post some of my own work for critique. But as a fellow artist, I can give you some general pointers based on your work and the reference material you provided.
1. Your explosion doesn't seem to get very bright, despite you using bright colors in 4 frames out of the 11. Perhaps add more frames for the flash and explosion part.
2. The reference you provided seems like it's a shell landing and exploding, based on the upward thrust of the explosion. I'm imagining it's a mortar shell. I think making your explosion have a bigger upward thrust would make it more dramatic and add impact.
3. Perhaps add some ground particles being pushed away by the explosion. That seems to add to the impact of the reference explosion you provided.
I hope these suggestions help. I think your first attempt is a strong one and it shows you studied the reference material well. Right now it works as a small explosion, from a grenade or some sort of small explosive. Keep up the good work man, I like all the work you've posted so far.