difficulty with battles

You can read our article on how to dodge here:
https://pokemongo.gamepress.gg/how-to-dodge

It takes some experience to get a feel for how long attacks last so maybe watching recorded battles and then practicing a bit would be helpful.

go on youtube and watch prodigynation use a butterfree to take down a 2800 dragonite

People who are good at dodging advocate dodging everything. Dodging just the charge moves is what I'd recommend working on first, as that will get you more benefit with fewer successful dodges. Then move on to trying to dodge everything.

I highly recommend checking Out Trainer Tips. It's a YouTube channel that most people here are familiar with I guess. One of his videos is called "How to dodge perfectly in Pokémon Go gym battles". Do I need to say more?

The "Yellow flash" could also be described as a bunch of yellow lines around the edge of the frame extending outward, kind of like in a comic book. It takes some practice to see and anticipate as the animation is distracting.
The problem that I have run into with dodging everything is the timer. In some matches you can run out of time. I have found it to be an obstacle most often in training when using under powered mon for maximum prestige gain or to use up some bums that I plan on transferring.

Just a matter of time and fighting experience. You'll be soon able to read the fighting screen like a kindergarten book. :)

While you work on your technique to dodge everything, you can focus on simply dodging charge moves. Personally I don't watch for the flash so much, instead I focus on the defender. When it's about to attack it will stop reacting to your quick strikes. And if it's about to do a charge attack, it will pause a bit longer before starting its attack (which is when you'll see the yellow flash). By anticipating the beginning of the attack by looking for earlier cues, the yellow flash become much easier to see.

Hope that helps.

IMO, the only real skill that's needed in this game besides dodging (I've seen terrible dodgers), is candie and dust management to achieve optimal result. Time, walking and knowledge of typing is not a skill.